Robust extension tone ringer with volume and pitch controls and an on/off switch. Connection to the exchange line is via either screw terminals or modular socket. Unit has a built-in speaker. An optional 15 watt horn speaker (connected via screw terminals) is available for more directional signalling of incoming calls. Maximum volume 98dB. This unit has a REN of 1.9. Dimensions 115(W) x 155(H) x 35(D)mm.