Digital bus communications system

A time division multiple access communications system, comprising:

• A. a digital bus including a pair of oppositely-directed, unidirectional digital signal paths interconnecting a common location with one or more remote locations,
• B. a connector network at said common location and adapted to receive digital signals in one or more uniform time slots associated with the inbound path, said time slots being in a repetitive framed sequence, and further adapted to transmit corresponding digital signals in one or more corresponding time slots associated with the outbound path,
• C. a plurality of terminals, each terminal being coupled to the inbound and outbound paths at one of said remote locations, and having an associated address and
• wherein each terminal includes means to idenfity and receive correspondingly addressed digital signals in contention ones of time slots on said outbound path, and
• wherein each terminal of a first set of said terminals includes contention transmission means for transmitting addressed digital signals in contention time slots on said inbound path, and
• D. signal collision detection means including at each first set terminal:
• i. monitoring means operative following transmission of a message signal by said terminal in a contention time slot to monitor the corresponding contention time slot on said outbound path to detect the presence of a signal corresponding only to said transmitted message signal,
• ii. re-transmission means responsive to said monitoring means to re-transmit said message signal in a subsequent contention time slot only when said monitoring means fails to detect the presence of said corresponding message signal in said corresponding contention slot.