Ah yes Paul, the old Wireless Intercom on two different Phases problem!.
I got sworn at, a few years ago when a customer bought a w/less Intercom from the retail shop of where I work and I was told that my company sold nothing but cheap junk
(at NZ$199?!).
I went and had a look and that's what it was, one socket-outlet on the Red Phase and the other on the Blue Phase!.
Never did get an apology, but what the heck, the customer is always right, eh!. [Linked Image]