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Tuesday, February 5, 2008

Telephone Receiver

An interesting circuit for a me- dium performance handy electronic telephone receiver, suited for receiving incoming calls, is described here. This circuit can be connected to almost all types of telephone exchange lines. To simplify the gadget, the dialler section has been omitted. The circuit can be constructed on a medium size veroboard. Wiring and components layout are not very critical. For compactness, enclose the wired circuit in a plastic cabinet as shown in Fig.(a) here. In order to prevent undesired acoustic feedback, it is necessary to adjust the orientation of ear-piece (LS) and mouth-piece (MIC) at the final stage of construction. The circuit consists of four sections: ringer, voltage regulator, transmitter and receiver. The ringer section is built around capacitor C1, resistor R1 and electronic buzzer BZ1.

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