D&R's passive Telephone Hybrid-1 is an interface between a standard analog telephone line and a mixing console. Its purpose is to enable to record or broadcast a conversation between a caller and a presenter in an easy way. Excellent audio separation between in and outgoing signals are achieved by carefully designed internal circuitry. It is a problem solver for changing two wire communication into a four wire system with separate in and outputs. The unit is housed inside a 9.5" metal frame. Input and outputs are on jacks and phone connections on RJ-11 connectors. It is a reliable and stable unit that doesn't need any external power.