We bought the Amprobe / Pascar model 300 Circuit Tracing kit, back in 1996.
Cost about $85,000,000 back then (actually it cost about $800).
It works excellent!
Usable from 6-600 Volts AC or DC.
Receiver has multiple set points for tracing in a variety of ways.
Cost now is likely to be at least Â½ of the 1996 price, which in my opinion is very well worth it.
I have used other types of tracers (except the Greenlee model mentioned previously by others), and found them to be less than useful for accurate Circuit Tracing, but very handy as a Paperweight or Doorstop.
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!