LOCAL HYBRID COMMUNICATION NETWORK IN CIRCUIT AND PACKET MODES WITH A TIME-MULTIPLEX LOOP

摘要

A hybrid local communication network operates both in circuit and packet modes with a loop carrying a TDM multiplex for interconnecting a number of terminals connected to the loop. The communications in a packet mode are controlled by a token. The header of each packet comprises the address of the called station and the address of the calling station. The TDM multiplex is arranged in multiframes comprising N frames O-(N-1). Each frame comprises P byte time slots iTO-iT(P-1) for transmitting a packet per frame. The byte time slot iTO in each frame contains the frame alignment pattern of the frame, the byte time slot iT1 contains the frame packet token byte, the byte time slots iT2-iTh contain the packet header, the byte time slots iT(h+1)-iTx contain the useful data of the packet, and the byte time slot iT(x+1)-iT (P-1) contain circuit type communication data. The service and supervision messages between any of the units, on one hand, and the loop control unit, on the other hand, are exchanged in packet mode. The digital value of x may be changed by the loop control unit which then transmits the value of x in a packet mode to every operative unit. The consecutive frames in a dialogue in packet mode between two units are used alternately by those control units involved in the dialogue, the time interval iTx of each frame being allotted to the acknowledgment transmitted by one control unit to the other control unit relating to the packet the one control unit received in the preceding frame.