CIRCUIT CUE - A must for any Serious Mobile DJ
CIRCUIT CUE + KLEIN or Gardner Bender Tester are two devices you need for testing AC electrical circuits.

Test the receptacle outlet for power and detect wiring problems before you connect..
Instructions:
1. Plug the (KLEIN or Gardner Bender) tester into each receptacle being tested to vertify the circuit is on and wired correctly.  
2. Then plug the Circuit Cue into a receptacle outlet.
3. With an IEC cable plugged into the bottom of the Circuit Cue, use an extension cord to access an ACreceptacle away from the original receptacle plug that the circuit cue is plugged into.
Note: When the light is ON  you have two separate circuits/breakers.

Edited video from Dec 20, 2023

Edited video from May 3 posting:

Note Never trust anyone's cables but your own! : Complete DJ Barr video link

You Tube video posted by Sonido Wolverin USA

Receptacle Testers

The circuit cue detects electrical phases and thus breakers from 2 phases 240V (120v on each phase)

Note: The Circuit Cue will not detect separate breakers if on the same phase.  Only if on separate phases

The benefit of two separate phases is that it gives you noise isolation which is desired in a Pro performance event thus the Circuit Cue works great for this application, while helping balance the electrical panel for heavy loads.

Great Video understanding neutral and ground relationships and why a tester is good to have.

How many outlets on a circuit breaker?