Digital data communication network and control system therefor

Claim 1

A communications network for providing half-duplex data communication between a central control station and a plurality of groups of remote terminal stations comprising: a first simplex communication channel connected to said central station for receiving and conveying signals therefrom; a second simplex communication connected to said central station for conveying signals thereto; a plurality of remote control units, one for each of said groups connected in parallel to said first and second simplex communications channels and to a plurality of serially connected terminals and comprising; first means for receiving signals from said first simplex communication channel and selectively transmitting signals from said series connected terminals to said second simplex communication channel, second means for detecting a first control signal directed to a single selected control unit and responsive thereto for causing said first means to transmit signals from said terminals, third means responsive to the received signals from the central station for detecting a general address recognizable by all devices connected to said network, fourth means responsive to the received signals from the central station for detecting a second control signal, fifth means responsive to said second and fourth means when a remote control unit is selected for interrupting the signal path between said first means and the series connected terminals and transmitting predetermined signals to said terminals during a first predetermined period of time, and sixth means responsive to said third means when a remote control unit is not selected for interrupting the signal path between the first means and the series connected terminals and transmitting said predetermined signals to said series connected terminals during a second predetermined period of time.