To provide a relay contact alarm output circuit in which the signals of a master station alarm, a slave station alarm and a system alarm can be outputted with less relays for output.

The relay contact alarm output circuit for monitoring the output of relay contact alarms from a master station device and a slave station device comprising an optical transmission system is composed of a relay 101 for MU- ALM earth output and a relay 102 for SU-ALM earth output connected with a master station alarm signal input port 111 and a slave station alarm signal input port 121, master station alarm signal output ports #1 and #2 (112 and 113) and slave station alarm signal output ports #1 and #2 (112 and 113) are formed from NC ports 3, NO ports 5 and COM ports 6 of the relays 101 and 102 on one side, and system alarm signal output ports #1 and #2 (132 and 133) are formed from free contacts.