SPEECH UNIT OF TELEPHONE SET Russian patent published in 1994 - IPC

FIELD: telephone communication equipment. SUBSTANCE: speech unit of telephone set has microphone 1, earphone 2, dial 3, first and second resistors 4 and 5, first capacitor 6, diode 7, first and second transistors 8 and 9, second capacitor 10, third resistor 11, third, fourth, fifth, sixth and seventh resistors 12-17. Under speech mode constant voltage is fed from collector of transistor 9 via earphone 2 to supply terminals of dial 3 and further on via resistor 17 to transistor 11 which provides for negative voltage feedback. Signal from microphone goes into line via two amplification stages built on transistors 11 and 9. Dialing of a number is accomplished by pulse mode of transistor 11 which makes or breaks stub of subscriber's line is loaded only to high-resistance dial. EFFECT: simplified design by reduction of number of components with preservation of performed functions. 1 dwg