Eddy Bergman.com: Simple but effective Transistor Curve Tracer circuit.
Wire Tracer (Transmitter)
em415Pro Automotive Electrical Power Probe Short/Open Circuit Finder Circuit Tester Tracer Cable Wire Breaker Tracker Circuit Fault Finder Car Open Short Wire Finder: Amazon.com: Tools & Home Improvement
Short circuit tracer/finder uses low power
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Signal Tracer and Injector - circuit diagrams, schematics, electronic projects