Our intercom - which allows five flats in a shared building (owned by some of the residents) to talk to the caller via telephone and buzz them in using a button on the handset in each flat - is no longer working properly. Callers can buzz the flats, but only a couple of the flats can unlock the door for them, and none of the telephones allow residents to talk to the caller. I believe the model is a Videx 3113 and I’ve been advised that it is likely a wiring issue.