Patent ID: 6084961
Filing Date: 2000-07-04
Classification: H04M

Abstract:
A circuit for monitoring battery voltages in a telephone terminal facility comprising:a ringing detection circuit for generating one of a short-time pulse signal and a long-time pulse signal at a ringing-detecting output terminal thereof in response to one of an off-hook signal and a ringing signal;a power detecting circuit for detecting voltages of the batteries and being provided with an enable terminal for controlling an operation of the power detecting circuit and an output terminal, said enable terminal being connected to the ringing detection output terminal of the ringing detection circuit and activated only by a signal transition at the ringing detection output terminal; anda latch being in series connection with the output terminal of the power detecting circuit, wherein an output terminal of the latch being set to be a voltage-detecting output terminal, a clock pulse input terminal thereof being connected to said ringing detection output terminal of the ringing detection circuit and a reset terminal thereof being connected with a second inverter for resetting the latch, said latch being triggered by a signal transition at said ringing detection output terminal to load an output state of the power detecting circuit into said latch and then said output state being latched therein;whereby the power detecting circuit being connected to one of a power source and said ringing detection output terminal of the ringing detection circuit through a first inverter by using a switch so that the status of the battery voltages is detected in one of an off-hook state or a ringing state.