I brought two Radioshack Wireless intercoms with me that worked great in the US. We are in a two story townhouse and my wife has to yell loud to get my attention, she is pregnant and I don't like her having to go up an down too much. I purchased 2 220 to 110 100 watt transformers for use with the units which say 6 watts on the back. I had to break off the ground connectors on the intercoms, as these transformers only have the 2 connections on them. I found that the units power on and the red led is on but they are not transmitting? Is this because of the missing ground. What if I connect a wire from the ground on one unit to the ground on the other and use a single power source to power both units? The problem is I do not know which connection if any of the two wire system in use here is correct for ground on these units. If I knew that I could make sure I connect it correctly and use a ground. I'm afraid I will short out the units if I get it wrong.