The RY-ES is a relay used to activate an external signaling device when the door station calls in. It can be used for call extension on the JK, JF, JA, KC, KB, AX, NEM, DB, and IE systems. The relay connects to the chime output of the master in place of the IER-2. The systems power supply powers the input of the RY-ES relay. A separate power source is required for the external device.