dial address signalling where no power can be supplied by the telephone subscriber 39 s line bipolar solid state circuitry may be used to provide the necessary backup power supply during these periods application_number US 69820785 A description referring now to fig2 the circuitry of the present invention is shown in its typical application connected to the tip and ring inputs of a telephone subscriber 39 s loop to a voltage regulating circuit and to an associated logic signal control input designated 34 bpe 34 battery power enable input resistor r1 and capacitor c1 form a low pass filter whose input is the telephone subscriber 39 s line via diode bridge cr1 and the hookswitch hs 1 the filter 39 s output is coupled to npn transistor q3 by either diode cr3 or by means alternatively of a direct connection the collector and emitter 39 s circuits for transistor q3 are filter capacitor c2 representing the output for the v dd supply and emitter resistor r3 respectively common emitter npn transistor q1 is driven by the 34 bpe 34 logic signal via a voltage divider made up of resistor r4 and resistor r8 the collector of transistor q1 is tied to the base of transistor q3 so that a logic 34 high 34 at the bpe input enables the battery power supply the aforementioned emitter resistor r3 is also connected to the base of pnp transistor q5 the emitter of transistor q5 is connected to the emitter of npn transitor q2 whose collector is tied to the output of the v dd supply the base of transistor q2 is.