Circuit for monitoring battery voltages of telephone terminal facility, using power detector temporarily activated by ringing or off-hook signal

摘要

A circuit for monitoring battery voltages of a telephone terminal facility is disclosed. This circuit mainly includes a ringing detection circuit for generating a pulse signal in response to an off-hook signal or a ringing signal, a power detecting circuit for detecting battery voltages and a latch being in series connection with the power detecting circuit for outputting a signal showing a status of the detected battery voltages. The power detecting circuit and the latch are of an edge-triggered type and are activated only when a handset of a telephone is picked up or a ringing signal is received so that both the consumed power and the voltage variations are low.