A data processing system includes a data processing unit and a number of communication units for coupling a corresponding number of terminal devices for transmission and reception of signals over a number of communication lines. Apparatus checks the operation of the communication units and includes logic...http://www.google.fr/patents/US3943348?utm_source=gb-gplus-shareBrevet US3943348 - Apparatus for monitoring the operation of a data processing communication system
Apparatus for monitoring the operation of a data processing communication system
