Handheld tone generator and cable tracer
Martin Rowe -- Test & Measurement World, 12/1/2002
Model 262, B&K Precision, Placentia,
CA.
714-237-9220; www.bkprecision.com
 |
|
Figure 1 |
The Model 262 kit includes a receiver and a transmitter (the unit with the wires in Figure 1). The transmitter's alligator clips connect to one end of a suspect wire pair, and its RJ-11 phone jack plugs into a socket. The transmitter transmits a pulsed audio signal into a wire; upon detecting the signal, the receiver amplifies it so you can hear it.
 |
|
Figure 2 |
The transmitter uses a tone generator (Figure 2a) to produce an 800-Hz tone that changes duty cycle (Figure 3). An amplifier boosts the signal to about 7.5 V, which excites the wire. The wire becomes a transmitting antenna, producing a magnetic field around it.
The receiver (Figure 2b) contains an antenna embedded in its case; when the antenna comes in proximity to the excited wire, it produces a current. A bandpass filter reduces interference from other frequencies before an amplifier boosts the signal to audible levels for the speaker.
The transmitter also contains a mode selector switch that connects an LED between the transmitter's probes. If you connect the probes across shorted wires and select continuity mode, the LED will light.
 |
|
Figure 3 |
