???? If you mean an echo, it can happen when someone is transmitting, and another radio is receiving the audio at the same time and it's inadvertantly being picked up by the mic (for example, if 2 people were relatively close to one another...) There's a very slight delay in when the audio is processed by the controller from the 2nd source, hence the echo effect. I've seen this happen on occasion on the ham bands, too.
73s Mike
