The polling features of a resident hybrid fiber/coax (HFC) network platform are used to poll between a link a hybrid digital terminal (HDT) and a network interface unit (NIU). In the absence of a polling response from the NIU to a polling query from the HDT, the polling is regarded as unsuccessful. Hence,...http://www.google.co.uk/patents/US6009079?utm_source=gb-gplus-sharePatent US6009079 - Method for measuring HDT-NIU availability
