Hi, I have 2 consumer wireless intercom boxes. That work perfectly under certain conditions. Hold that thought.

I rent 2 adjacent shops in one building, each with it's own master AC master breaker box. When I plug-in the 2 intercoms in the same shop they work. Either shop (doesn't matter). But when I plug-in 1 intercom in each seperate shop they don't work. Here's where the mystery deepens...

If I run a 10 meter extension cord from one shop to the other (thus essentially plugging the intercoms both into the same AC line). They work perfectly. (So it's not a distance issue, it's not an interference issue... heck, I even have line-of-sight through glass.)

I'm clever, so I assumed maybe the 2 shop's circuits were out-of-phase... So I had my electrician reverse the incoming + and - to the main breaker. No luck!

Hopefully someone here can help me solve this mystery and puzzle.

I uploaded a photo of one of the intercoms, standing in the doorways of my 1st shop, looking at the 2nd shop.

 

Simple. One intercom is plugged into a L1 120V circuit outlet, the other is plugged into a L2 circuit outlet. The RF carrier doesn't want to travel all the way to the pole pig and couple through the 240V center tapped winding on it...

 

Yeah sounds like those communicate over the power lines. Each shop might be on a different leg of a 3 phase service for even load distribution. You might need to get one that uses radio communication.

 

Yeah sounds like those communicate over the power lines. Each shop might be on a different leg of a 3 phase service for even load distribution. You might need to get one that uses radio communication.

We are saying the same thing. Those things wont even make it to the other side of the center tap on a given phase, let alone to a different phase entirely.

 

Funny thing... they used to work fine, just recently they stopped working. What could have changed?

 

We are saying the same thing. Those things wont even make it to the other side of the center tap on a given phase, let alone to a different phase entirely.

Does it make any difference that the manufacture says it's a 4 channel FM transmitter/receiver?

 

that only tells you that it uses FM to transmit.
misleading to be sure, but still true. It just transmits over AC wiring and not over the air.

 

So you've solved your problem: Connect an extension cord between the two shops.

 

So you've solved your problem: Connect an extension cord between the two shops.

lol... that cord goes out one door and in the other... not too practical

 

a small wire will do. extension cord needs to carry over 12 amps. If you can insure it will not be used as a power source for AC power tools and the like, then a small cable could be extended to get the intercom on the same circuit. maybe over head through the ceiling?