Telephone pickup preampliifer

Posted on Feb 5, 2014

Here is a simple circuit based on IC uA 741 that can be used to pickup voice from telephone lines without even contacting the line. If a high impedance magnetic core is placed near a telephone instrument or near one of the telephone wires, it picks up inductively both sides of the telephonic conversation without any electrical contact. A preamplif

Telephone pickup preampliifer
Click here to download the full size of the above Circuit.

ier based on IC uA741 is used to pickup these signals. The circuit is nothing but an inverting amplifier whose gain depends on the feedback resistance R4. The Op-Amp produces the necessary gain to drive the headphone. The circuit can be used as a telephone bug too.

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