Transformerless transistorised telephone subscriber appts. - has transistor amplifier connected as tone generator via cradle contact

摘要

The transformerless, transistor circuit for telephone subscriber appts. in two-party line systems consists of a terminating network formed from resistors (R2, R3) together with a line balancing resistor and capacitor network (R4, R5, C7). In the diode bridge at the a and b line inputs to the appts. two links are provided (B1, B2) which may be removed for conversion to party-line use. The receivers transistor amplifier has its base connected to a change-over contact (GU2) operated by the cradle switch. In place of a bell, the transistor may be converted to a tone oscillator by means of a network (C8-10, R11, 12) connected to the base via the cradle contact.