An electronic device enters pattern data upon activating a matrix of keys with a finger. A comparing section compares measured data in a counter (register C) for measuring the time interval from the release of a key till the depression of the next key, with a value set in a memory (register E) for storing...http://www.google.co.uk/patents/US4654874?utm_source=gb-gplus-sharePatent US4654874 - Electronic device with a finger activating data input function
