DIALING CIRCUIT

PURPOSE:To effectively prevent a spark and an arc in case when a dial contact is opened and closed, by intermitting a DC loop current by a contactless switching circuit, intermitting a control current of the contactless switching circuit by a mechanical dial contact, and sending out a dial pulse. CONSTITUTION:When a dial is free-moved, a dial impulse contact 1 repeats its opening and closing by the number of the dial numerals, and simultaneously the second switching circuit 8 repeats turn-on and turn-off, therefore, a dial pulse is sent out to a switchboard by intermitting a DC loop current. In this case, a dial short contact 2 is closed in the course of dialing, is opened when dialing ends, turns off the circuit 8, and releases the short circuit of a calling circuit 4. Subsequently, when the contact 2 is opened, a signal current is all supplied to the first switching circuit 7 through the dial impulse contact 1, therefore, the circuit 7 is turned on, and a DC current flows to the circuit 4, by which a call can be executed.