A simple device that can be used to give a signal or to operate an electrical apparatus every time the telephone rings. Very useful for noisy places, where a light signal or a siren can draw the attention to the phone better than the telephone bell, or for cases where the telephone is in such a place that cannot be heard and you need a secondary bell. It does not require any power supply and the relay contacts are rated at 250V 2A. Suitable box: 2122.