A.W. Sperry CS550A Circuit Breaker Finder
Circuit Breaker Finder.  By using a transmitter and receiver, this circuit breaker finder quickly and easily identifies individual branch circuits at the panel box without interrupting power.  It is the best way to accurately locate circuit breakers.  They are compact in size and extremely easy to use.  UL listed to both US and Canadian standards.  Locates AC Breakers or Fuses.  No need to interrupt Power.  Distinctive Signal, Audible and Visual Indication.  Does not interfere with sensitive electronic equipment.   Uses one 9V battery not included.  Includes one transmitter and one receiver.