Volume adjusting circuit for ringing transducer of telephone - connects different outputs of controller to earth via different resistances depending on position of push button indicating desired volume

摘要

The circuit includes a control (ST) with inputs (4) and outputs (1,2,3). The controller (ST) analyses the incoming call signals on the connection line and generates the sound signals for the electroacoustic transducer (W) driven by an amplifier (T2,T3). The volume of the transducer is adjusted in dependence on the operation of a button (TA) connected to the controller (ST). The sound signal output (T) of the controller (ST) is connected to the base of a transistor (T1). One output (1) of the controller (ST) is directly connected to the emitter. Other outputs (2,3) are connected to the emitter via resistors (R2,R3) of different values and an earthed resistor (R4). The collector of the transistor (T1) is connected via a resistor (p1) to the operating voltage (+U1) and to the amplifier (T2,T3) controlling the transducer. The controller (ST) earths one of the outputs (1,2,3) corresp. to the desired volume, in dependence on the state of the button (TA). ADVANTAGE - Simple, inexpensive and reliable.