| 摘要 |
A system for monitoring the operating condition of one or more reporting devices, which incorporates a telephone network connecting a remote terminal and a monitor terminal. A control circuit is provided in which one or more monitor relays are interposed, each monitor relay opening independently in response to a change in operating condition of a reporting device. When a monitor relay opens, current flow is interrupted to a return signal control relay, which thereby short-circuits the subscriber loop to the remote terminal, so that a busy signal is returned in response to calls from the monitor terminal. When all monitor relays are closed, indicating all reporting devices to be in normal condition, the return signal control relay is energized, opening the short circuit in the subscriber loop. Accordingly, a ringing signal is returned in response to calls to the remote terminal.
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