Voice messages and eventual alarm signals are sent on a single unipolar line (a conductor). These devices can therefore be used both as intercoms and as alarm buzzers, using only a single conductor. The intervention of an alarm can interrupt a conversation, which can be reactivated by releasing and pressing the “speak” button again.
It is possible to activate the “speak / listen without hands” mode, permitting communications even with one’s hands full. Up to 5 devices can be connected on the same line.
