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Tape Recorder By Telephone Controlled

2014-12-16 21:24  
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A circuit for energizing and de-energizing a relay to start and stop a tape recorder receiving an endless tape loop provided with an electrically conductive foil disposed on a portion thereof. The circuit includes a capacitor in series with the relay so that when an energizing member is activated, the capacitor which is initially charged is then discharged across the relay to start the tape recorder and thereby cause movement of the endless tape loop.This circuit converts a tape recorder into a completely automatic telephone conversation recording instrument that needs no external power source. Voltage at the switch terminals of tape recorder applied to a pair of Darlington-connected transistors, Ql and Q2, will turn on and start the tape recorder. To turn the transistors off, and thereby stop the machine, apply a negative voltage to the base of Ql from the phone line.When the telephone receiver is on the hook, there is typically about 50 volts dc across the phone divided across Rl, R2, and R4 in such a way that the base of Ql is sufficiently negative to keep the tape recorder off. When the phone`s receiver is picked up, the voltage on the telephone line drops to about 5 volts, which leaves-insufficient negative voltage on the base of Ql to keep it cut off, so the tape recorder starts and begins to record.When a tape recorder is set under a sound recording mode, only a record terminal RE of a logic control circuit 1 is set at level "0". Therefore the discrimiwww.lw20.comnation signal of an output terminal 6 is set at level "1" together with discrimination signals of other output terminals 3W5 set at level "1" respectively.
 

Telephone-controlled tape starter