WO1998057456A1 - Multiple computer data channels, video, audio, and/or telephone signals in a single transmission medium - Google Patents

Abstract

An analog technique and system is described which combines multiple computer communication (50), video (52) and/or audio (54) information for simultaneous bi-directional communication over a single signal transmission line. Bi-directional simultaneous communication of multiple computer channels on a single carrier is also described. Local oscillators are synchronized such that the transmit carrier is recovered and used in the receiver of the system to demodulate the information residing in the carrier side bands. Techniques for utilizing active termination of a transmission line to create a zero impedance, virtual ground receiver node is also described.

Description

MULTIPLE COMPUTER DATA CHANNELS, VIDEO, AUDIO, AND/OR TELEPHONE SIGNALS IN A SINGLE TRANSMISSION MEDIUM

Background of the Invention 1. Field of the Invention.

This invention relates to a system and method for transmission of multiple computer channels, video, audio and/or telephone signals over a single signal transmission medium. 2. Discussion of Related Technology.

At present, the deployment of computer, video, audio and telephone communications over a signal transmission medium, which may be a current conducting transmission medium, or may be a non-current conducting transmission medium, is accomplished by utilizing multiple individual coaxial cables, twisted wire pairs, or optical fibers, for each signal in a system, i.e. a single cable for computer communications, a single cable for video communications, a single cable for audio communications, and a single twisted wire pair for telephone communications. Installation of such a system involves the use of these multiple cables, each specifically designed for the type of signals to be conducted therein. Each such cable must be individually installed, terminated and tested for signal propagation acceptance. Obvious disadvantages of such a system are the great complexity, the large quantity of material needed to employ the installation, the high cost of installation and the limited transmission pass length in each cable without a repeater to pass a signal further along the cable.

A need exists for a system which integrates the transmission of multiple computer communication signals, video signals, audio signals and/or telephone signals in a single signal transmission medium. Such a system would practically eliminate the cost of cable installation by utilizing existing wiring in a facility, whether the wiring be twisted pair wires, coaxial cable or optical fibers. Additionally, the need exists for a current conducting signal transmission system which can transmit these various described forms of information (computer, audio, video, etc.) over relatively long distances of up to several kilometers without requiring repeaters, which also results in great cost savings.

Summary of the Invention The present invention allows discrete multiple computer data channels, an audio channel, a video channel, and/or a telephone channel to be broadcast together over a single existing signal transmission medium, without the need for multiple cables, repeaters or digital signal processors. There is a tremendous unmet demand for such a system and methodology to provide a single cable communication broadcast utilizing these signals, where the system and methodology utilizes existing coaxial cable, twisted wire pairs or fiber optic cables which are extant in schools, office buildings, and other pre-wired facilities. Since current conducting and non- current conducting cables already exist in these facilities, a tremendous cost savings of material and labor is achieved by foregoing the rewiring of these facilities with additional individual signal cables to provide the infrastructure for transmission and reception of each of these various types of signals.

Specifically, the following problems in the art are solved: a) The direct reduction of the number of cables required to connect a group of computers, multi-media sites, or multi-media processes or access points at some distant location to a hub, switch, router, point transceiver or patch bay for further signal distribution is achieved; b) The distance signals can be communicated is greatly increased using a modulation scheme to encode the various computer, video, audio and/or telephone channel signals into an amplitude modulated (AM) frequency distributed wide-bandwidth radio frequency (RF) communication broadcast using single side band (SSB) modulation, or using quadrature amplitude modulation (QAM); c) Reduction of space allocations and costs for equipment closets and installation points by consolidating, and thus, reducing the number of cables in an equipment locker or closet is achieved; and d) Building costs are reduced by reducing the number of cables in a building. This results in conduits, ducts, lockers, vaults, and closets for wiring being smaller and the walls thinner. More square footage in the building would be available for habitation. The weight of the building itself is decreased, and all the associated costs (bigger foundation, more materials, extensive engineering, etc.) also are decreased.

Without limitation, several novel aspects of the system and method of the present invention are, but are not limited to: a) simultaneous bi-directional communication of multiple dissimilar data channels over a single signal transmission medium; b) use of a single bi-directional communications port at each end of a single signal transmission medium to facilitate signal transfer from or to the medium, to or from, respectively, an external device or another signal transmission medium; and c) use of a single carrier to simultaneously transmit and receive multiple data channels over the single signal transmission medium.

Brief Description of the Drawings FIG. 1 schematically depicts an embodiment of the interconnectivity of the LAN utilizing the present invention; FIG. 2 illustrates an embodiment of a remote user connection port, or a central connection port;

FIG. 3 schematically illustrates a frequency distribution of signals over a plurality of channels;

FIG. 4 illustrates the frequency distribution of an embodiment of the transceiver channel of the present invention;

FIG. 5 illustrates the frequency spectrum for an embodiment of the transceivers of the present invention;

FIG. 6 schematically illustrates a block diagram of the operation of an embodiment of the transceiver of the present invention; FIG. 7 schematically illustrates a block diagram of how the output carrier frequency is removed on the input of one embodiment of the transceiver of the present invention;

FIG. 8 is a block diagram of an embodiment of the MODEM; FIG. 9 is a block diagram of an embodiment of the RF manager and the

RF transceiver head;

FIG. 10 schematically illustrates an embodiment of SLOT; FIG. 11 schematically illustrates a carrier recovery method and system; FIG. 12 schematically illustrates an embodiment of a bi-directional port having a current sink; and

FIG. 13 schematically illustrates another embodiment of a bi-directional port having a current sink.

Detailed Description of the Preferred Embodiments The United States Government has announced an ambitious goal is to provide computers in every school in America to help educate children with computer literacy, and to help children in their general studies utilizing the computer as a form of teaching aid. To accomplish this lofty goal, schools must possess a signal transmission infrastructure having sufficient signal bandwidth to be able to provide multiple computer data channel communication. The present system and method utilizes existing current conducting signal transmission media, such as coaxial cable, twisted wire pairs, or utilizes existing non-current conducting signal transmission media, such as optical fiber, to provide the desired multiple computer data (Ethernet) channel communication capability. In general, the present system and method can be implemented in any pre-wired facility. The present system and method also provides communication of video, audio, and/or telephone channel data over the same existing medium, simultaneously with the computer data channel communication. Herein, the term "channel" shall mean a data channel which may include computer (Ethernet) formatted data, audio data, video data, or telephone formatted data. The present invention includes the use of a unique modulation scheme which provides data communication in an individual simultaneous bidirectional asynchronous (ISBA) format, utilizing multiple computer channels, a video channel, a bi-directional audio channel, and/or a telephone channel, over a single transmission medium, which may be a current conducting signal transmission medium, such as a coaxial cable or a twisted wire pair, or may be a non-current conducting signal transmission medium, such as an optical fiber. A single common carrier frequency is utilized to amplitude modulate a plurality of these channels to provide simultaneous bi-directional communication, where the information resides in the carrier side bands. In essence, a private radio spectrum is created and utilized by the present method and system.

FIG. 1 illustrates an embodiment of the interconnectivity of the present system. Each individual remote location 44, denoted Remote 1 - Remote N, which may each be a classroom within a school, an office within an office building, or any other remote user location within a pre-wired facility, includes at least one remote user connection port 34. FIG. 2 shows a remote port 34 in greater detail.

Referring to FIG. 2, a remote user connection port 34 is shown. Port 34 is preferably a wall-mounted connector device having a front end which includes various individual connectors adapted to connect to a computer, a TV set, a monitor, a NCR, a telephone, or an intercom. The connectors facilitate bi-directional communication of computer, video, audio, telephone, and other information. The connectors are mounted on the front side of port 34 which would mount flush with the surface of a wall within a remote location 44. Each remote location 44 may include one or more of these wall mounted remote user ports 34. The port 34 would also include processors 18a and b, and 22a and b, of FIG. 6, as well as the modulator 12, demodulator 14, SLOT 20 and transceiver head 16 circuitry of FIG. 6.

The proximal end 39 of medium 32 is connected to transceiver head 16 of port 34. A plurality of computer connectors 50, which are preferably bidirectional Ethernet connections, are provided on the wall-mount front side of port 34. A bi-directional video connector 52, bi-directional audio connector 42 and telephone connector 56 is also provided. As previously mentioned, each central connection port 38, which is connected to each remote user port 34 via medium 32, is preferably identical to the remote user connection port 34. Each remote user port 34 has a back side which connects, through transceiver head 16, to a proximal end 39 of an individual medium 32, where each medium 32 is a twisted wire pair, a coaxial cable, or any other current conducting signal transmission medium for communicating electrical signals, or is a non-current conducting optical fiber. For optical fiber medium 32, transceiver head 16 would be an opto-electrical interface.

The distal end 40 of each individual medium 32 connects to a central connection port 38 which is located in a central distribution center (CDC) 42 on an equipment rack or other similar storage device. This CDC 42 may be located in an audio/video equipment room or data closest within a school, factory or office building. Each port 38 is similar to, and preferably identical to, the user connection port 34 of FIG. 2.

The remote locations 44, media 32 and CDC 42 form a signal transmission system 30 which facilitates simultaneous bi-directional signal communication of a mix of signals which include the computer channels, and the audio, video, telephone or other bi-directional channels. Selected central connection ports 38 in the CDC 42 may be connected to a server or to an Ethernet hub to facilitate Ethernet computer channel communication between the respective remote user ports 34 which have their central connection port connected to the server or to the Ethernet hub. In this manner, computers located in the remote locations 44 connected to a remote user port 34 within the respective remote location 44, which port 34 in turn has been connected to a server or a hub, may communicate with each other via E-mail or other computer communication protocol in an ISBA format.

Also, for example, a video tape may be inserted into a NCR located in the CDC, or in any remote location 44, and the signal may be broadcast to any remote user port 34 within the system 30. Additionally, computer communication over the Internet may be accomplished by connecting selected remote locations 44 through the CDC 42 with external Ethernet or telephone connections which connect to external communications link 36. Video or audio information from a satellite may also be connected to selected remote locations 44 via external link 36. One of skill in the art can envision other possible combinations of connections between selected remote locations 44 and other remote locations 44, or between selected remote locations 44 and an external communication source and medium which connects to link 36.

The external communications link 36, which connects via external interface 46 to any external communication source, such as a telephone line, a fiber optic cable, a cable TV (CATN) cable, a satellite receiver or transmitter, or an Ethernet connection, facilitates bi-directional or uni-directional communication between the remote user ports 34 of system 30 and the external communication medium via the CDC 42. Referring to FIG. 3, the RF spectrum for each of the plurality of transceivers used to provide the ISBA communication of the various channels is illustrated. The RF spectrum of Transceiver 1 through Transceiver Ν is shown. The channels, respectively, occupy different portions of the Radio Frequency (RF) spectrum. In this embodiment, there may be guard bands 20 (FIG. 4) between any two adjacent channels.

FIG. 4 illustrates the general composition of a transceiver spectrum. As shown in FIG. 4, each transceiver spectrum includes bandwidth for a lower side band 24 and for an upper side band 26. In addition, a central carrier 24 may be employed with the side bands. There is also bandwidth set aside for one or more reference carriers, or pilot tones, 18 (FIG. 3) for signal synchronization, which will be explained in further detail below.

FIG. 5 illustrates the preferred transceiver frequency spectrum for the system 30, where three transceivers, 72, 74 and 76, each 30 MHz wide, are shown centered on carrier frequencies of 40 MHz, 80 MHz and 120 MHz, respectively. A lower and upper side band, each 15 MHz wide, designated as L and U respectively, is shown flanking each respective carrier. The low frequency information block 70 preferably includes the non-computer channels, such as cable television (CATN) signals, audio signals, telephone signals, and/or a pilot synchronization signal 18 (FIG. 3).

The CATN signals may originate from a television set, a NCR, or from an external CATN transmission line connected to external communications link 36 (FIG.l). The CATN signals may be provided to a television set or a monitor. The telephone signals may originate from a telephone, or from an outside telephone line connected to external communications link 36. The telephone signals may be provided to a telephone, or to the outside telephone line. The audio signals may originate from or be provided to an intercom located in select remote locations 44.

Each RF transceiver spectrum shown in more detail in FIGS. 3 and 5, is implemented using the architecture shown in FIG. 6, which is, in effect, a small two-channel bi-directional radio station operating on an assigned frequency, which creates a private radio spectrum for the channels. In the preferred embodiment, the carriers 24 (FIG. 4) employed will maintain a harmonic relationship with each other such that the distortion products associated with any one carrier will coincide with the fundamental frequency of the other carriers, where the carrier frequency distribution will not generate energy in any of the data side band frequencies, shown in FIGS. 4 and 5. Achieving simultaneous bi-directional two-channel operation over a single carrier while utilizing two side bands implies that either a double Single Side band (SSB) AM scheme, or a Quadrature Amplitude Modulation (QAM) scheme, is employed. In the case of double SSB AM, the upper and lower side bands each include a single channel. The local oscillator signal for modulating the channels in modulator 12 is the same local oscillator signal used to demodulate the two channels in demodulator 14. In the case of QAM, the combined quadratured sum of two channels exist on one side band and the quadratured difference will reside in the other side band, which allows for simultaneous bi-directional communication of two channels on a single carrier, but only when the modulator 12 and demodulator 14 use the same local oscillator signal or carrier for both channels. For either scheme, as shown in FIG. 4, a single carrier is employed where both side bands are assigned to each direction of data flow.

Although not a preferred modulation scheme, bi-directional communication of a single channel using a simple traditional Amplitude

Modulation (AM) scheme could be utilized, where both side bands are necessary to carry portions of a single channel. Using this technique, only one channel per carrier is possible for ISBA communication. Therefore, for example, for communication of six channels, six carriers and six transceiver spectrum (FIG.3) would be required. Such an AM scheme requires twice the bandwidth of a double SSB AM or a QAM scheme, described above.

Frequency Modulation (FM) techniques could also be employed using dual side bands to achieve ISBA communication of a channel using a single carrier. But, costly filters and more complex modulation and demodulation circuitry would be required to accomplish the same result as the less complex double SSB AM or QAM schemes discussed above.

Referring to FIG. 6, the basic functions of each multi-channel transceiver 10 is shown. Channel signals to be output over signal transmission medium 32 enter the transceiver 10 on input lines Chi In and Ch2 In. The transmit processor blocks 18a and b and receive processor blocks 22a and b, together with modulator 12 and demodulator 14, are part of MODEM 200 (FIG. 8). RF transceiver head 16 is shown in more detail in FIG. 9. The synchronized local oscillator technology (SLOT) block 20 is part of RF manager 100 of FIG. 9. The channel signals to be output to the medium 32 are transmitted to medium 32 via the RF transceiver head 16. Conversely, channel signals are received from medium 32 via transceiver head 16 and are provided as output signals Chi Out and Ch2 Out from transceiver 10 via receive processor blocks 22a and b.

Referring to FIG. 9, multi-channel RF transceiver head 16 is utilized, which includes a transmitter 11 and receiver 13. A RF manager 100, which includes a signal distribution block 110 and a carrier synchronization and signal processing (CSSP) block 120, communicates with transceiver head 16.

A multi-channel modulator/demodulator (MODEM) 200 (FIG. 8) communicates with RF manager 100 and includes a modulator 12 and a demodulator 14, where modulator 12 and demodulator 14 use the same carrier and are locked in phase. MODEM 200 processes a plurality of input channels Chi In and Ch2 In and a plurality of output channels Chi Out and Ch2 Out. The modulator 12 shall preferably include a fixed carrier and operate as a master to which the demodulator 14 is preferably locked, making demodulator 14 a slave oscillator. In another embodiment, an independent master oscillator can be used to define the channel transmit carrier frequency for modulator 12. In a further embodiment, a modulator 12, having a slave oscillator, shall operate in the suppressed carrier mode, producing only side bands. In general, demodulator 14 may operate in a synchrodyne or autodyne mode, or may be hetrodyned, such that the demodulation process operates at the same carrier frequency as does the modulation process for that transceiver.

As shown in FIG. 8, the multi-channel input signals Chi In and Ch2 In are provided from a remote port 34 (FIG. 1) from individual computers, telephones, or other external devices located within a remote location 44 connected to that remote port 34, or may be provided from a central connection port 38 (FIG. 1) from CDC 42 or from external interface 46 which is connected to that central connection port 38. In any event, interface blocks 25a and b provide bi-directional flow of signals being received from and provided to a port 34 or a port 38 to which the MODEM 200 is connected. These interface blocks 25a and b are signal dependent. Depending on the makeup of the input and output signals, these blocks 25a and b interface with and account for the particular electrical requirements required to match with the device to which it is connected.

For example, a standard RS-170a video signal channel is provided 75 ohm line loading and a driving stage by blocks 25a and b. For Ethernet channels, an IEEE 803.2 standard isolation transformer is provided. For an audio channel, a balanced input and output is provided. In general, all signal types have standard formats defining levels, impedance and connectivity characteristics, as well as physical standards for the mechanical interconnection of the wires or optical fibers employed, which are accounted for by blocks 25a and b.

The transmit processors 18a and 18b act on the respective input signals to perform, among other functions, the functions of correctly terminating the signals, limiting the frequency or power of the signals, equalizing the frequency, phase group delay or harmonic relationships of the signals, compressing or decompressing the signals, or otherwise prepare the signals for the modulation process of modulator 12.

The multiple channel signals are then modulated by modulator 12 using a single carrier, where Chi In data is preferably modulated with the sine of a selected carrier signal to create an intermediate frequency (IF) signal Chi RF Out. Signal Ch 2 In is preferably modulated with the cosine of the same selected carrier signal to create an IF signal Ch2 RF Out. The two modulated channel signals are then provided to RF manager 100, shown in FIG.9. Thus, the selected carrier signal used by MODEM 200 modulator 12 to modulate the channel 1 and channel 2 signals are preferably 90 degrees out of phase with respect to each other.

For signals received by transceiver head 16 from transmission medium 32, the received modulated signals are provided to MODEM 200 by RF manager 100. Channel 1 and channel 2 signals are demodulated by demodulator 14 using the same selected carrier, or local oscillator signal, as used by modulator 12, where the modulator 12 carrier is either a fixed master, or a slave carrier, or is a recovered carrier. The fixed carrier and carrier recovery schemes are discussed below. Similar to the modulation process, channel 1, which is a modulated intermediate frequency (IF) signal, is preferably demodulated by demodulator 14 with the sine of a single local oscillator signal, or carrier. Channel 2, which is also a modulated intermediate frequency (IF) signal, is preferably demodulated by demodulator 14 with the cosine of the same local oscillator signal, or carrier. Thus, the local oscillator signal, or carrier used by MODEM 200 demodulator 14 to demodulate the channel 1 and channel 2 signals are also 90 degrees out of phase with respect to each other. Demodulated channel 1 and channel 2 signals are then processed by receive signal processors 22a and b, which act on the respective signals to perform, among other functions, the functions of correctly terminating the signals for their connection to a remote user port 34 or to a central connection port 38. These processors 22a and b also perform the functions of, limiting the frequency or power of the signals, equalizing the frequency, phase group delay or harmonic relationships of the signals, compressing or decompressing the signals, or otherwise preparing the signals for being output to the respective port 34 or port 38 to which the MODEM 200 is connected.

As mentioned above, modulator 12 of MODEM 200 may produce a quadrature amplitude modulated (QAM) signal for two channels and one carrier, which in one embodiment has a lower side band L which includes the composite signal CHX + CHY, and upper side band U which includes the composite signal CHX - CHY, where X and Y are separate channels. In other embodiments, the formulation of the upper and lower side bands is reversed. QAM is preferably accomplished using a quadrature modulator, a MAX 2452 by Maxim Integrated Products of Sunnyvale, CA. In this one-carrier, two-channel example, ChX is Chi In and ChY is Ch2 In. Thus, for transmission of QAM signals for channels 1 and 2, a transceiver 10 (FIG. 6) would be centered at a first frequency, preferably 40 MHz, having a lower sideband of CH 1 + CH2 and an upper side band of CHI - CH2.

Similarly, if additional channels 3 and 4 were to be transmitted, an additional multi-channel MODEM 200 having its own multi-channel transceiver 10 would be centered at a second frequency, preferably 80 MHz, having a lower sideband of the composite signal CH3 + CH4 and an upper side band of the composite signal CH3 - CH4. For additional channels 5 and 6, an additional multi-channel MODEM 200 having its own multi-channel transceiver 10 would be centered at a third frequency, preferably 120 MHz, having a lower side band of the composite signal CH5 + CH6 and an upper side band of the composite signal CH5 - CH6.

Audio, telephone, CATN, or other channel signals would be centered around additional carriers at frequencies preferably less than 20 MHz. Of course, other center carrier frequencies could be selected for any of the QAM transceivers so long as sufficient bandwidth is allowed for between the carriers to support the upper and the lower side bands which include the data being transmitted over each respective multi-channel transceiver 10. In this example, the lower side band 22 signal for the 40 MHz transceiver is preferably formed in accordance with the following equation:

IF(in-phase signal for lower side band 22) = sin (CH1TX) sin (40 MHz) + sin (CH2TX) cos (40 MHz). The upper side band 26 for the 40 MHz transceiver is formed in accordance with the following equation: IF(in-phase signal for upper side band 26) = sin (CHITX) sin (40 MHz) - sin (CH2TX) cos (40 MHz). Demodulation of lower side band 22 for the 40 MHz transceiver is preferably accomplished according to the following equation:

IF(demodulated in-phase signal for lower side band 22 ) = sin (40 MHz) (sin (CH1RX) sin (40 MHz) + sin (CH2RX) cos (40 MHz)). The demodulation of upper side band 26 for the 40 MHz transceiver is preferably accomplished according to the following equation:

IF(demodulated in-phase signal for upper side band 26 ) = sin (40 MHz) (sin (CH1RX) sin (40 MHz) - sin (CH2RX) cos (40 MHz)). Demodulation is preferably accomplished by a quadrature demodulator, a MAX 2451 by Maxim Integrated Products of Sunnyvale, CA.

As stated previously, modulation and demodulation of any of the channels can be accomplished using a carrier selected at any frequency, as long as sufficient bandwidth is allowed between the carriers for the corresponding side bands of each carrier and the associated guard bands. The above equations would apply for any of these selected carriers for QAM applications. For double SSB AM mentioned above, each multi-channel transceiver 10 of each MODEM 200 would assemble a composite signal for a respective pair of channels where the respective transceiver 10 would be centered at a first frequency, similar to the QAM scheme, but each of the side bands for that carrier would include data from only a single channel, either channel X or channel Y.

In the present example, system 30 preferably provides for simultaneous bi-directional communication of six Ethernet channels (channels 1-6) using only three carriers centered at 40 MHz, 80 MHz and 120 MHz, respectively. Data for each of these channels is being simultaneously modulated and transmitted onto medium 32 by a transceiver 10 connected to each end of medium 32 of system 30. Additionally, audio, video and/or telephone channels are being simultaneously modulated and transmitted over medium 32 on other carriers. The total sum of these modulated dissimilar signals being simultaneously transmitted from both ends of medium 32 form a unified modulated signal

(UMS) which is present on medium 32. Since data for a given channel is being simultaneously transmitted at the same frequency in each direction over medium 32, each transceiver 10 must be able to discern from the UMS the data to be received from medium 32 for that particular channel. To accomplish this, only the data flowing to the transceiver from the other end of medium 32 is desired. Data for the same channel flowing from the same transceiver for transmission to the transceiver on the opposite end of medium 32 is ignored.

To capture only the receive data for the channel requires a two-part process. First, the signal received by receiver 13 of transceiver 10 must be demodulated by demodulator 14, with the carrier recovered from the received signal corresponding to that channel. Second, the demodulated received signal may then have subtracted from it data for the same channel which is to be transmitted by the same transceiver 10. The demodulation scheme will be explained below. FIG. 7 depicts a one-channel example of the data subtraction from the received demodulated signal. Here, the demodulated channel signal for channel one, which includes both transmit and receive information for channel one, is provided to the non-inverting input node 17 of subtractor 15. Subtractor 15 is preferably a dual input LT 1193 Video Difference Amplifier by Linear Technology Corp. of Milpitas, CA. Channel one data to be transmitted by that transceiver to medium 32 is provided to the inverting input node 19 of subtractor 15. The subtractor output 21 represents the desired receive data for channel one. Thus, in general, the input data of system 30 is not seen at the output for the respective channel, which results in high channel signal-to-noise performance directional isolation. The key to simultaneous bi-directional communication of a single channel using the same carrier at each end of medium 32 is the synchronization of all carriers, or local oscillators, by the synchronized local oscillator technology (SLOT) block 20 of RF manager 100 (FIG. 9). Maintaining the frequency and phase relationships between the respective carriers permits the implementation of bi-directional simultaneous communication and affords a high degree of immunity from inter-channel cross-talk, distortion and noise. To this end, it is preferred that all frequency generation will be keyed to a single pilot tone, or synchronization carrier 18, which is injected into signal adder 102 of RF manager 100 (FIG.9). To implement simultaneous bi-directional communication over a single carrier, utilizing the SLOT block 20, it is essential that the local oscillator, or demodulator 14, of a receiving transceiver 10 be precisely locked to the received carrier on a cycle-by- cycle basis. This allows for exact synchronous demodulation of high speed side band information accompanying the carrier, which increases the accuracy of the demodulation process by taking advantage of the common induced noise and distortion extant in the carrier and data information. Additionally, phase-synchronous suppressed carrier side bands are created for transmission on the same carrier as that received, which facilitates simultaneous transmission and reception on the same carrier. The transmit carrier, which is actually the carrier recovered from the received signal for a channel, or is a multiple of that recovered carrier, is generated by carrier recovery block 54 of RF manager 100. If a fixed master clock is to be used as a pilot tone, or master carrier 18 for the transmit signal for a channel, a clock 50 is used to generate that fixed master carrier which is provided to transmit frequency multiplier block 56. The fixed carrier is multiplied withing multiplier block 56 such that a plurality of transmit carriers is produced, which are in turn provide to individual modulators. As stated previously, all carriers are harmonically related and are multiples of the original fixed pilot tone 18.

Using a recovered carrier to demodulate and modulate a channel at the same frequency lowers distortion and noise on the received signal and makes possible synchrodyne-type bi-directional data transmission on the same carrier, without the use of phase-locked loops (PPLs) to stabilize the local oscillator modulator. A disadvantage of PPLs is that they utilize a time constant for locking the signals to be recovered, which does not permit a cycle-by-cycle lock required by the present system and method. Instead, PPLs implement a time- averaged synchronization, which ignores cycle-by-cycle noise anomalies. To achieve exact carrier synchronization, such anomalies cannot be ignored. Additionally, PPLs typically lock a local oscillator in the receiver circuit to the received signal through the use of phase comparison on the received signal and the locally generated local oscillator signal. Errors introduced into the overall received signal (carrier and side bands) while being transmitted via medium 32 are not common to both the recovered carrier and the side bands, since a PPL inherently injects a small degree of carrier frequency drift or jitter (a byproduct of the continual re-locking process of the PPL) which results in a cycle-by- cycle phase error in the recovered signal. Also, a PPL recovery system has inherent low immunity to both amplitude and frequency noise which results from the connectivity aspect of the transmission process. These noises or errors are the result of frequency or phase (Doppler, multi-path, etc.) and amplitude (induced, lightning, etc.) noises which are either directly or indirectly added to the propagated signal, and thus, the received signal. Referring to FIG. 10, SLOT block 20 of FIG. 6 operates such that the carrier for the received channel signal is isolated and then amplified. This isolated and amplified carrier then becomes the new local oscillator, or carrier, for both synchrodyne reception using demodulator 14 and same frequency transmission using modulator 12. The functional components of carrier recovery block 54 (FIG.9) of SLOT block 20 are depicted in FIG. 11.

Referring to FIG. 9, a fixed pilot signal 18 is injected into adder 102 to be added with the other modulated signals. Typically, the modulated signals have a suppressed carrier, so injecting pilot 18 is necessary so pilot 18 may be received at the opposite end of medium 32 possessing the same frequency and phase anomalies as the transmitted channel data. The output of adder 102 is UMS 104, which is then provided to transmitter 11 of transceiver head 16 for output over medium 32. Carrier recovery block 54 isolates the recovered injected pilot carrier 18 from medium 32. The received pilot 18 is then utilized directly, or is multiplied by frequency multipliers blocks 56 or 58 to provide the various carriers utilized for modulation and demodulation of the channel information. As explained elsewhere herein, no PPLs are used to generate the carrier from the received signal.

Referring to the carrier recovery block 54 of FIG. 11, the entire received signal is provided to an amplifier 60. The amplified received signal then passes through a limiter circuit 64 and a narrow band filter 68 which extracts the original recovered carrier. As a result, the recovered carrier contains the same frequency or phase noise as the side band modulation information. Thus, in essence, induced errors are tracked in the side bands on a cycle-by-cycle basis. The primary novelty of this carrier recovery approach is that the method described is specifically designed to retain frequency and phase errors induced into the carrier by the transmission and connectivity processes. More specifically, the errors contained in the carrier are temporally and characteristically the same as those induced into the side bands which contain the transmitted channel. Referring to FIG. 9 the function and operation of RF manager 100 is described. The basic task of RF manager 100 is to interface multiple MODEMs 200 to the transceiver head 16. In performing this function, RF manager 100: receives as input signals, modulated channel signals output from the MODEMs 200; provides as output signals, modulated channel signals received from medium 32; supplies the transmit carriers for the modulators 12 and the demodulation local oscillator or carrier signal for the demodulators 14; processes all signals; and provides special functions such as local oscillator phase control and carrier recover.

Modulated channel signals are output from MODEMs 200 and are input to RF manager 100. These signals are provided to adder 102 where they are summed to produce a UMS 104. An pilot carrier 18 may also be provided to adder 102 to form part of the UMS 104. The UMS 104 is then amplified by gain stage 106. The amplified UMS is then provided to transceiver head 16 to be transmitted by transmitter 11 over medium 32.

The UMS is received by receiver 13 of transmitter head 16 and is provided to carrier recovery block 54 and to distribution block 112.

Distribution block 112 divides up the UMS into channel signals which are provided to a MODEM associated with the particular channel. Block 112 may include filtering and automatic or manual level adjustment of the channel signals before they are provided to the MODEMs. The received UMS is processed by the carrier recovery block 54 as described above, to isolate the recovered carrier.

The transmit frequency multiplier 56 receives either: the recovered carrier from carrier recovery block 54, if operating in the slave mode; or, a fixed pilot carrier from clock 50, if operating in the master mode. In either mode, the received carrier signal is multiplied by a selected factor in multiplier 56 to produce a plurality of carriers of higher frequency, all of which are harmonically related to the input signal which was multiplied. A separate one of these multiplied carrier signals is provided to a modulator 12 of a MODEM 200 associated with that carrier frequency for the particular channels it will modulate. The receive frequency multiplier 58 receives only the recovered carrier from carrier recovery block 54. It always operates in the slave mode. The received recovered carrier signal is multiplied by a selected factor in multiplier 56 to produce a plurality of carriers of higher frequency, all of which are harmonically related to the input signal which was multiplied. A separate one of these multiplied carrier signals is provided to a demodulator 14 of a MODEM 200 associated with that carrier frequency for the particular channels it will demodulate.

Phase adjustment block 60 provides a phase adjustment of selected multiplied recovered carrier signals if the recovered carrier signal and the transmit master pilot signal are not locked in phase. This correction overcomes the effects of group delay distortions created by the length of the medium 32 between the transmitter on one end of medium 32 and the receiver on the other end. Generally, transceiver head 16 functions as a two-way port to the outside world for the RF manager 100. Transmitter 11 outputs the UMS 104 from adder 102 to medium 32. Receiver 13 takes energy out of medium 32 in such a way as to optimize the performance of the medium 32, removes the locally generated UMS leaving only data from the transceiver at the opposite end of medium 32, and delivers the received channel data at a proper level to the RF manager 100 for distribution to the MODEMs 200.

Referring to FIG. 12, a technique for transmitting energy into the transmission medium 32 is accomplished at the proper line sourcing impedance Rzout, satisfying a back-terminated transmission line technique. At the same time, medium 32 is terminated in a zero impedance virtual ground at the inverting input node of receiver 13, which is a current-mode receiver. These termination techniques are not used for a non-current conducting signal transmission medium, such as optical fiber. This bi-directional signal flow termination technique allows bi-directional information transfer while taking advantage of the extended frequency response provided by the active load technique illustrated. The output of transmitter 11, a line driver, is connected to medium 32 through a back-termination resistive element Rzout. The resistive element Rzout, preferably a passive resistor, is selected to approximate the impedance value of the medium 32. A signal received from medium 32 is provided to the current summing inverting input node of the current-mode receiver 13. The inverting input node of the current-mode receiver 13 is also connected to resistive element RZin to voltage neutralize, or zero, the inverting node creating a virtual ground. To prevent the zeroed inverting node from loading down the medium 32 during information transmission, the current-mode receiver 13 is referenced to the signal to be transmitted by providing the signal to be transmitted to the non-inverting input node of the current-mode receiver 13. This produces a subtraction of the signal to be transmitted from the received signal. Thus, the signal output from current-mode receiver 13 is the desired received channel signal. FIG. 13 illustrates another embodiment of a termination scheme for a current conducting signal transmission medium. Here, a virtual ground, zero impedance point is created at the inverting input node of current-mode receiver 13. The value of Rzl is selected to equal the value of Rz2, which makes the impedance of medium 32 irrelevant. This embodiment has the distance advantage of allowing the impedance of medium 32 to vary from one application to another, as the physical length of medium varies from application to application. Additional factors affect the impedance of the transmission medium 32, such as changes due to temperature variation, mechanical stress, vibration, age or manufacturing variation. The zero impedance, virtual ground inverting node of current-mode receiver 13 of the embodiment in FIG. 13 or FIG. 14 performs as a current sink to allow medium 32 to absorb all the radio frequency energy carried by the medium 32, thus offering no reflected standing wave (RSW) energy. An ideal transmission line termination is thereby emulated. Additionally, the current sink function compensates or equalizes the operating characteristics of the active receiver 13 to correct the output signal for losses or distortions caused by medium 32 being terminated. Referring to FIGS. 13 and 14, preferably the active signal is taken off medium 32 through current-mode receiver 13, which is preferably a very high speed amplifier having an inverting gain stage.

Operating in the current-mode allows the gain of the receiver 13 to be dependant on the effective input resistance to the receiver 13. Here, that input resistance is the impedance of the signal line to which the receiver 13 is connected.

The foregoing disclosure, description and examples are illustrative an explanatory of the preferred embodiments. Changes in the size, shape, materials, elements and individual components used, the connections made, or other construction, may be made without departing from the spirit and scope of the invention herein claimed.

Claims

What is claimed is: CLAIMS

1. A communications system which combines computer data, and video data, audio data, or telephone data, and provides said data over a signal transmission medium, comprising: a) a signal transmission medium; b) a remote user connection port, including at least one computer connection, and at least one audio connection, at least one video connection, or at least one telephone line connection; and c) a central connection port, including at least one computer connection, and at least one audio connection, at least one video connection, or at least one telephone line connection; wherein computer data, and audio data, video data or telephone data is communicated between said remote user connection port and said central connection port via said medium.

2. The system of claim 1, wherein said signal transmission medium comprises a current conducting signal transmission medium.

3. The system of claim 1, wherein said signal transmission medium comprises at least one optical fiber.

4. The system of claim 1, wherein at least one said audio connection at said remote user connection port and at said central connection port supports bi- directional data communication.

5. The system of claim 1, wherein at least one said video connection at said remote user connection port and at said central connection port supports bi- directional data communication.

6. The system of claim 1, wherein at least one said computer connection at said remote user connection port and at said central connection port supports an Ethernet computer transmission protocol.

7. The system of claim 2, wherein said current conducting medium comprises at least one twisted wire pair.

8. The system of claim 2, wherein said current conducting medium comprises a coaxial cable.

9. The system of claim 1, wherein said data is being communicated in an individual simultaneous bi-directional asynchronous (ISBA) format.

10. The system of claim 1, further comprising a distribution unit which includes said central connection port.

11. A communications system which combines computer data, and video, audio or telephone data, and provides said data over a signal transmission medium comprising: a) a plurality of cables, each said cable comprising a signal transmission medium; b) a plurality of remote user connection ports, each said remote port comprising at least one computer connection, and at least one audio connection, at least one video connection, or at least one telephone line connection; c) a plurality of central connection ports, each said central port comprising at least one computer connection, and at least one audio connection, at least one video connection, or at least one telephone line connection; and d) a distribution unit, wherein each of said plurality of central ports is connected to said distribution unit via a separate one of said plurality of cables; wherein computer data, and audio data, video data or telephone data is communicated between each said plurality of remote ports and said central ports via a separate one of said plurality of cables.

12. The system of claim 11, wherein said cables comprise at least one coaxial cable.

13. The system of claim 11, wherein said cables comprise at least one twisted wire pair.

14. The system of claim 11, wherein said cables comprise at least one optical fiber.

15. The system of claim 11, wherein at least one said computer connection at each said remote user connection port and at each said central connection port supports an Ethernet communication protocol.

16. The system of claim 11, wherein said distribution unit is configurable such that connections to an external: computer network, audio channel, video channel or telephone network, are selectively connected via said cables to selected ones of said plurality of central connection ports.

17. The system of claim 11, wherein selected ones of said plurality of central connection ports are selectively connected to each other via said distribution unit.

18. The system of claim 11, wherein said data is communicated having a qudrature format centered around a carrier frequency.

19. The system of claim 9, wherein said data being communicated is modulated using amplitude modulation (AM).

20. The system of claim 9, wherein said data being communicated is modulated using double SSB AM.

21. The system of claim 18, wherein said data being communicated is modulated using QAM.

22. The system of claim 18, wherein said data being communicated is modulated using FM.

23. The system of claim 11, wherein at least one of said audio and video connections supports bi-directional data communication.

24. A method of interfacing between a multi-channel bi-directional communications medium and an external communication device, comprising the steps of: a) interfacing between an external device and a multi-channel bi- directional communications port; b) inputting signals from said external device through said communications port to form input signals; c) processing said input signals for output over a bi-directional signal transmission medium; d) modulating said processed input signals using a first carrier; e) outputting said modulated input signals to said medium; f) demodulating signals input from said medium using a second carrier; g) processing said demodulated signals for output to said external device; and h) outputting said processed demodulated signals to said external device.

25. The method of claim 24, wherein said communication port is a dual- channel communication port.

26. The method of claim 24, wherein said signal transmission medium is a current conducting medium, and wherein said step of interfacing is accomplished using an isolation transformer.

27. The method of claim 24, wherein said signal transmission medium is a current conducting medium, and wherein said step of interfacing is accomplished using an impedance line termination.

28. The method of claim 24, wherein said step of processing said input signals includes attenuating said input signals.

29. The method of claim 24, wherein said step of processing said input signals includes phase shifting said input signals.

30. The method of claim 24, wherein said step of processing said input signals includes signal compression of said input signals.

31. The method of claim 24, wherein said step of processing said demodulated signals includes attenuating said demodulated signals.

32. The method of claim 24, wherein said step of processing said demodulated signals includes phase shifting said demodulated signals.

33. The method of claim 24, wherein said step of processing said demodulated signals includes signal compression of said demodulated signals.

34. The method of claim 24, wherein said first carrier and said second carrier are the same carrier.

35. The method of claim 34, wherein said same carrier is a recovered carrier.

36. The method of claim 24, wherein said first carrier is a fixed carrier.

37. The method of claim 24, wherein said second carrier is a recovered carrier.

38. A modulator/demodulator (MODEM) circuit, comprising: a) an interface circuit having a bi-directional input port and a bi- directional output port; b) a transmit signal processing circuit having an output and having an input connected to said interface circuit; c) a transmit mixer having an output and having an input connected to said transmit signal processing circuit; d) a receive mixer having an input and an output; and e) a receive signal processing circuit having an output connected to said interface circuit bi-directional output port and having an input connected to said receive mixer output.

39. The circuit of claim 38, wherein said interface circuit includes a transmission line termination circuit.

40. The circuit of claim 38, wherein said interface circuit includes a line driver circuit connected to said bi-directional input port.

41. The circuit of claim 38, wherein said interface circuit includes an isolation transformer.

42. The circuit of claim 38, wherein said interface circuit includes a plurality of data channels.

43. The circuit of claim 42, wherein said data channels are Ethernet computer channels.

44. The circuit of claim 38, wherein said transmit signal processing circuit includes signal attenuation circuitry.

45. The circuit of claim 38, wherein said transmit signal processing circuit includes signal gain circuitry.

46. The circuit of claim 38, wherein said transmit signal processing circuit includes signal phase shift circuitry.

47. The circuit of claim 38, wherein said transmit signal processing circuit includes signal compression circuitry.

48. The circuit of claim 38, wherein said transmit signal processing circuit includes signal decompression circuitry.

49. The circuit of claim 38, wherein said receive signal processing circuit includes signal attenuation circuitry.

50. The circuit of claim 38, wherein said receive signal processing circuit includes signal gain circuitry.

51. The circuit of claim 38, wherein said receive signal processing circuit includes signal phase shift circuitry.

52. The circuit of claim 38, wherein receive signal processing circuit includes signal compression circuitry.

53. The circuit of claim 38, wherein said receive signal processing circuit includes signal decompression circuitry.

54. The circuit of claim 38, wherein said transmit mixer modulates a plurality of data channels with a first carrier.

55. The circuit of claim 54, wherein said receive mixer demodulates a plurality of data channels with a second carrier.

56. The circuit of claim 55, wherein said first carrier and said second carrier are the same carrier.

57. The circuit of claim 56, wherein simultaneous bi-directional communication of multiple data channels on a common carrier is accomplished.

58. A modulator circuit for modulating a plurality of data channels, comprising: a) an interface circuit having an input port; b) a transmit signal processing circuit having an output and having an input connected to said interface circuit; and c) a transmit mixer having an output and having an input connected to said transmit signal processing circuit; wherein said transmit mixer modulates a plurality of data channels which are input to said interface circuit from said input port using a single local oscillator signal; and wherein a transmit signal output from said transmit mixer output comprises a modulated plurality of data channels having a single carrier.

59. The circuit of claim 58, wherein said interface circuit includes an isolation transformer.

60. The circuit of claim 58, wherein said interface circuit includes a transmission line termination circuit.

61. A demodulator circuit for demodulating a plurality of data channels, comprising: a) a receive mixer circuit having an input and an output; b) a receive signal processing circuit having an output and having an input connected to said receive mixer circuit output; and c) an interface circuit having an output port, and having an input connected to said receive signal processing circuit output; wherein said receive mixer circuit demodulator and modulated signal input to said receive mixer circuit input to produce a plurality of data channels; and wherein said receive mixer circuit utilizes a single local oscillator signal to demodulate said plurality of data channels from a single carrier.

62. The circuit of claim 61, wherein said interface circuit includes an isolation transformer.

63. The circuit of claim 61, wherein said interface circuit includes a transmission line termination circuit.

64. A method of interfacing between a plurality of MODEMs and a transceiver, comprising the steps of: a) inputting a plurality of individual modulated signals from a plurality of MODEMs; b) summing said plurality of modulated signals to form a unified modulated signal (UMS); c) providing said UMS to a transceiver for outputting by said transceiver onto a communication medium; d) inputting said UMS from said transceiver, wherein said UMS includes said summed plurality of modulated signals from step b) and includes other summed modulation input signals from an external source; e) separating said UMS from said transceiver into a plurality of individual modulated input signals; and f) outputting said separated individual modulated input signals to a plurality of MODEMs.

65. The method of claim 64, further comprising the step of recovering a carrier from said UMS input from said transceiver.

66. The method of claim 65, further comprising the step of multiplying said recovered carrier to produce a second recovered carrier.

67. The method of claim 65, further comprising the step of multiplying said recovered carrier to produce a plurality of recovered carriers.

68. The method of claim 67, further comprising the step of providing said recovered carrier and said plurality of recovered carriers each to a separate demodulator to demodulate said second UMS at a different frequency with each demodulator.

69. The method of claim 64, further providing the step of providing a fixed master carrier.

70. The method of claim 69, further comprising the step of multiplying said fixed master carrier to produce a second fixed master carrier.

71. The method of claim 69, further comprising the step of multiplying said fixed master carrier to produce a plurality of fixed master carriers.

72. The method of claim 71, further comprising the step of providing said fixed master carrier and said plurality of fixed master carriers each to a separate modulator.

73. The method of claim 67, further comprising the step of adjusting the phase of said recovered carrier and each one of said plurality of recovered carriers.

74. The method of claim 64, wherein said step of summing includes the step of providing a carrier to be summed with said plurality of modulated signals to form said UMS.

75. The method of claim 74, wherein said provided carrier is a pilot tone carrier.

76. The method of claim 74, wherein said provided carrier is a fixed master carrier.

77. The method of claim 74, wherein said provided carrier is a recovered carrier.

78. A system for providing multiple data paths over a single signal transmission medium, comprising: a) a signal transmission medium having a first end and a second end; b) a first modulator/demodulator (MODEM) circuit, wherein multiple data paths are provided to said MODEM circuit from one or more external devices to be output over said medium; c) a first signal processing and distribution circuit connected to said first MODEM circuit; and d) a first transceiver connected to said first signal processing and distribution circuit and to said medium first end; wherein said data paths to be output are modulated by said first MODEM circuit, wherein said modulated paths are summed by said first signal processing and distribution circuit to form a transmit unified modulated signal (UMS); and wherein said UMS is output onto said medium first end by said first transceiver.

79. The system of claim 78, further comprising a second transceiver connected to said medium second end.

80. The system of claim 79, further comprising a second signal processing and distribution circuit connected to said second transceiver.

81. The system of claim 80, further comprising a second MODEM circuit connected to said second signal processing and distribution circuit.

82. The system of claim 81, wherein multiple data paths are received by said second transceiver from said medium second end, are signal processed, and are output from said second MODEM circuit to one or more external devices.

83. The system of claim 78, wherein said one or more external devices is/are a computer.

84. The system of claim 82, wherein said one or more external devices is/are a computer.

85. The system of claim 78, wherein said first MODEM circuit comprises a modulator circuit and a demodulator circuit.

86. The system of claim 85, wherein said modulator circuit includes an interface circuit, a transmit signal processor and a mixer.

87. The system of claim 86, wherein said interface circuit includes circuitry which interfaces between said one or more external devices and said transmit signal processor.

88. The system of claim 86, wherein said transmit signal processor provides signal attenuation for said data paths to be output.

89. The system of claim 86, wherein said transmit signal processor provides signal gain for said data paths to be output.

90. The system of claim 86, wherein said transmit signal processor provides phase shifting for said data paths to be output.

91. The system of claim 86, wherein said transmit signal processor provides signal compression for said data paths to be output.

92. The system of claim 86, wherein said transmit signal processor provides signal expansion for said data paths to be output.

93. The system of claim 86, wherein said mixer modulates said data paths to be output using a single carrier.

94. The system of claim 78, wherein multiple data paths to be output are modulated by said first MODEM circuit using a single carrier.

95. The system of claim 94, wherein said single carrier is a recovered carrier.

96. The system of claim 85, wherein said demodulator circuit includes a mixer, a receive signal processor and an interface circuit.

97. The system of claim 96, wherein said mixer demodulates multiple data paths received by said first transceiver from said medium first end.

98. The system of claim 97, wherein multiple said received data paths are demodulated by said mixer using a single carrier.

99. The system of claim 98, wherein said signal carrier is a recovered carrier.

100. The system of claim 96, wherein said receive signal processor provides signal attenuation for multiple data paths received by said first transceiver from said medium first end.

101. The system of claim 96, wherein said receive signal processor provides signal gain for multiple data paths received by said first transceiver from said medium first end.

102. The system of claim 96, wherein said receive signal processor provides phase shifting for multiple data paths received by said first transceiver from said medium first end.

103. The system of claim 96, wherein said receive signal processor provides signal compression for multiple data paths received by said first transceiver from said medium first end.

104. The system of claim 96, wherein said receive signal processor provides signal expansion for multiple data paths received by said first transceiver from said medium first end.

105. The system of claim 96, wherein said interface circuit includes circuitry which interfaces between said receive signal processor and said one or more external devices.

106. The system of claim 78, wherein said first signal processing and distribution circuit includes a carrier recovery circuit, a transmit signal summation circuit, a received signal distribution circuit, a carrier multiplier circuit and a phase adjustment circuit.

107. The system of claim 78, wherein said first signal processing and distribution circuit includes a carrier recovery circuit.

108. The system of claim 107, wherein said carrier recovery circuit inputs a receive unified modulated signal (UMS) received by said first transceiver circuit from said medium first end, wherein said UMS comprises a plurality of modulated data paths.

109. The system of claim 108, wherein said carrier recovery circuit isolates a carrier from said receive UMS and provides said isolated carrier to said first MODEM circuit as a recovered carrier.

110. The system of claim 109, wherein said recovered carrier is utilized by said first MODEM circuit to modulate said data paths to be output.

111. The system of claim 78, wherein said multiple data paths to be output over said medium comprise Ethernet computer channels.

112. The system of claim 78, wherein said first MODEM circuit comprises a plurality of MODEM subcircuits, wherein each of said plurality of MODEM subcircuits modulates and demodulates two computer channels.

113. A system for providing multiple channels of information over a current conducting signal transmission medium, comprising: a) a current conducting signal transmission medium having a first end and a second end; b) a first modulator/demodulator (MODEM) circuit comprising a modulator circuit and a demodulator circuit, wherein multiple information channels are input to said modulator circuit, from one or more external devices, to be output over said medium first end; c) a first signal processing and distribution circuit connected to said first MODEM circuit; and d) a first transceiver connected to said first signal processing and distribution circuit and to said medium first end; wherein said information channels to be output are modulated by said first MODEM circuit; wherein said modulated information channels are summed together to form a transmit unified modulated signal (UMS); and wherein said UMS is output to said medium first end by said first transceiver.

114. The system of claim 113, wherein one or more audio signals are input to said first MODEM circuit from one or more external audio signal devices to be output over said medium, and wherein said one or more audio signals to be output are modulated by said first MODEM circuit to form a portion of said transmit UMS.

115. The system of claim 114, wherein said one or more external audio signal devices comprise an intercom.

116. The system of claim 113, wherein one or more video signals are input to said first MODEM circuit from one or more external video signal devices to be output over said medium, and wherein said one or more video signals to be output are modulated by said first MODEM circuit to form a portion of said transmit UMS.

117. The system of claim 113, wherein at least one said channel is input to said first MODEM circuit from said medium first end, and wherein said MODEM circuit then provides said at least one said channel to said one or more external devices.

118. The system of claim 113, wherein one or more telephone signals are input to said first MODEM circuit from one or more external telephone signal devices to be output over said medium, and wherein said one or more telephone signals to be output are modulated by said first MODEM circuit to form a portion of said transmit UMS.

119. The system of claim 116, wherein said one or more external video signal devices comprise a NCR.

120. The system of claim 117, wherein said one or more external video signal devices comprise a television.

121. The system of claim 117, wherein said one or more external video signal devices comprise a monitor.

122. The system of claim 118, wherein said one or more external telephone signal devices comprise a telephone.

123. The system of claim 113, wherein said modulator circuit and said demodulator circuit each operate using a recovered carrier.

124. The system of claim 123, wherein said recovered carrier is provided by a carrier recovery circuit which receives a unified modulated signal (UMS) received by said first transceiver from said medium first end, wherein said carrier recovery circuit isolates a carrier embedded in said received UMS, and wherein said received UMS includes multiple information channels modulated over a single carrier.

125. The system of claim 113, wherein said first MODEM circuit provides simultaneous bi-directional communication of multiple information channels on a single carrier.

126. A method of communicating electronic information over a signal transmission medium, comprising the steps of: a) modulating multiple data channels to be transmitted in a first direction over a signal transmission medium, wherein a unified modulated signal (UMS) is formed, and wherein a first carrier is used to modulate said multiple data channels to be transmitted in said first direction; b) outputting said UMS onto a first end of said medium; c) receiving said UMS at a second end of said medium; and d) demodulating said received UMS to form first received multiple data channels.

127. The method of claim 126, wherein said step of receiving said UMS includes isolating a carrier from said received UMS.

128. The method of claim 126, further comprising the steps of: e) modulating multiple data channels to be transmitted in a second directional over said medium, wherein a second carrier is used to modulate said multiple data channels to be transmitted in said second direction over said medium; f) outputting said modulated data channels to be transmitted in said second directional onto a second end of said medium to form a combined UMS; g) receiving said combined UMS at said first end of said medium; and h) demodulating said combined UMS to form second received multiple data channels; wherein said UMS received in step c) comprises said combined UMS

129. The method of claim 128, wherein said second carrier used to modulate said multiple data channels to be transmitted in said second direction is the same as said first carrier used to modulate said multiple data channels to be transmitted in said first direction.

130. The method of claim 126, further comprising the step of modulating a first audio signal to be transmitted in said first direction over said medium, wherein said modulated first audio signal comprises a portion of said UMS.

131. The method of claim 126, further comprising the step of modulating a first video signal to be transmitted in said first direction, over said medium wherein said modulated first video signal comprises a portion of said UMS.

132. The method of claim 126, further comprising the step of modulating a first telephone signal to be transmitted in said first direction over said medium, wherein said modulated first telephone signal comprises a portion of said UMS.

133. The method of claim 128, wherein simultaneous bi-directional communication is accomplished, wherein said multiple data channels modulated in step a) are the same multiple data channels as said data channels modulated in step e).

134. A method of communicating multiple pairs of data channels over a signal transmission medium, comprising the steps of: a) modulating multiple pairs of data channels to be transmitted in a first direction over a signal transmission medium, wherein each said pair of data channels is modulated with a separate carrier; b) summing said modulated multiple pairs of data channels to be transmitted in said first direction to form a unified modulated signal (UMS); c) outputting said UMS onto a first end of said medium; d) receiving said UMS at a second end of said medium; and e) demodulating said received UMS to form first received multiple pairs of data channels.

135. The method of claim 134, wherein a separate carrier is used to modulate each pair of said multiple pairs of data channels to be transmitted in said first direction.

136. The method of claim 134, wherein three pairs of data channels are modulated.

137. The method of claim 136, wherein said three pairs of data channels are modulated each with a separate carrier wherein said separate carriers are harmonically related.

138. The method of claim 136, wherein said three pairs of data channels are modulated, wherein each of said pairs of data channels has a separate carrier, and wherein said separate carriers are harmonically related.

139. The method of claim 134, further comprising the steps of: f) modulating multiple pairs of data channels to be transmitted in a second direction over said medium; g) summing said modulated multiple pairs of data channels to be transmitted in said second direction; h) outputting said summed modulated multiple pairs of data channels to be transmitted in said second direction onto said second end of said medium, forming a combined UMS; i) receiving said combined UMS at said first end of said medium; and j) demodulating said combined UMS to form second received multiple pairs of data channels; wherein said UMS received in step d) comprises said combined UMS.

140. The method of claim 139, wherein said carriers used to modulate said pairs of data channels in step a) are the same carriers used to modulate said pairs of data channels in step f).

141. The method of claim 126, wherein said signal transmission medium is a current conducting transmission medium.

142. The method of claim 134, wherein said signal transmission medium is a current conducting transmission medium.