PURPOSE: To improve reliability of double system by subjecting an auxiliary system to receive and monitor data at all times and reducing common circuit part between system under operation and the auxiliary system as far as possible.
CONSTITUTION: When a monitor station 1-1 communicates with a monitored station 6 from presently used monitor station 1-1 through N system transmission line while a presently used monitor station 1-2 is functioning as an auxiliary monitor station, gates S1-1, S4-1, S4-2 are closed and gates S2-1, S3-1, S1-2, S3-2 are opened. Under this condition, transmitted signals from the presently used monitor station 11 arrives at the monitored station 6 through the gate 1-1, a transducer 3-1, a light data way 4-1 and a transducer 5-1 and calling is effected. The reply signal from the monitored station 6 returns to the auxiliary monitor station 1-2 from the transducer 5-1, light data way 4-1, transducer 3-1, and at the same time, returns to the presently used monitor station 1-1 through the gate 4-2. Further, it returns to the presently used monitor station 1-1 through a transducer 5-2, the light data way 4-2, transducer 3-2. At the same time, it is supplied to the auxiliary monitor station 1-2 through the gate 4-1.
YONEMOTO EIJI
KUCHITSU NOBORU
IIDA HIROYUKI
