Communications system.

摘要

A communications system has a data highway made up of two optical communications channels (28,30) forming a ring to interconnect stations (10,11) whose signals are interfaced with the ring by an optical-electrical repeater (24,25). Each repeater (24,25) includes an optical detector (32) and an optical transmitter (39) for each channel and normally functions as a repeater except when the associated station is transmitting. A control element (31) can prevent the repeater from repeating and a line (33) is provided for receiving the transmitted signal at the transmitting station after it has gone around the ring (28) for checking the condition of the ring. The transfer of mastership is accomplished by grouping into a logical loop of high traffic stations those stations which must be serviced frequently, and the grouping into at least one other logical loop of low traffic stations those requring less frequent service. The token signifying mastership is passed from station to station in the high traffic loop at a maximum speed compatible with the work to be done by each station until a predetermined time period has lapsed since the mastership was passed through the low traffic group. Upon expiration of that time period, mastership is passed sequentially through the low traffic loop stations. Mastership is then returned to a previously determined high traffic loop station. Each local network has two metallic cables (20,22) providing redundant channels between stations (10,11) of a group, the redundant optical rings (28,30) forming the highway interconnecting those networks. The control element (31) connects the output of the detector (32) with the transmitter (39). A control signal supplied over one metallic line (35) from the station which is transmitting causes the control element (31) to disconnect the detector (32) and transmitter (39) to prevent operation of the combination as a repeater. The transmission is supplied over another metallic line (38) from the station to the transmitter (39) and thence around the ring until it is converted to an electrical signal at the corresponding detector (32). The resulting electrical signal is then conducted to the transmitting station over still another metallic line (33) for checking as a means for determining if the ring is complete.