The circuit depicted is the receiver device of a
transmitter/receiver combination that will prove extremely handy when tracing
the path of electrical wiring in a building or to locate a break in a wire. The
corresponding transmitter may be found elsewhere in this website. The
transmitter produces a distinctive tone which alternates between 2100 Hz and
2200 Hz. The matching receiver for the wire tracer is possibly even simpler than
the transmitter, as is shown by the schematic. It consists of no more than a
short wire antenna (a piece of wire, 10 cm long is adequate), a high-pass filter
(C1-R1), an amplifier stage (IC1), an output stage (T1) and a
loudspeaker.
The prototype
used a high impedance loudspeaker from a telephone handset, and this worked
remarkably well. The purpose of P1 is to adjust the amplification. At the
highest amplification, the wire energized by the transmitter can be traced from
several tens of centimeters away. A direct electrical connection is therefore
not required. However, it is important that you hold the ground connection
(earth) in your hand.
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