The 4WE&M module is a four-wire audio interface with E and M signaling interfaces. E and M is a type of supervisory line signaling that uses separate leads, called the E (ear) lead and the M (mouth) lead. In 4WE&M signaling, two wires are used to receive and two wires are used to transmit, incorporating simplex control and differential payload in each channel. The 4WE&M module supports type I, II, and V signaling.
The 4WE&M module provides the following features: