In an apartment with one button calling to an wall mounted phone in each suite, the phone started with hearing a crackle, which eventually disbled the microphone and speaker of the hand held. ...does this sound like to simply repair the problem, just replace the handheld? how does one troubleshoot an intercom like this? In the handheld there is a blue and red wire going to the earpiece, and the same blue and red wiore at the microphone, plus a white wire. the cradle itself releases the front door lock and it still works. ...any suggestions?