Off-hook signal and dial pulse generating circuit and a method for driving the same circuit

摘要

An off-hook signal and dial pulse generating circuit which has a smaller number of switching devices having a high withstand current characteristic and has a less surge voltage than up to now. A dial pulse circuit and a switch block circuit are connected in parallel with the output side of a full-wave rectifying circuit. The circuit comprises an impedance circuit and a first switch circuit to be turned on/off by a signal. The impedance circuit operates in a state where it has an inductance component in case that a signal synchronized with a signal is off and operates in a state where it has no inductance in case that the signal is on, and an electric current flowing therethrough is turned on/off by the first switch circuit. The circuit comprises a series circuit composed of second and third switch circuits. The second switch circuit is turned on/off in response to a signal synchronized with the signal (where this circuit is off when the signal is on). The third switch circuit is turned on/off in response to the signal.