E and M Signaling

E And M Signaling

E&M (earth & magneto, or ear & mouth) is a type of supervisory line signaling that uses DC signals on separate leads, called the "E" lead and "M" lead, traditionally used in the telecommunications industry between telephone switches.

E&M was originally developed to allow PABXs in different geographic locations to communicate over an analog private circuit. Some digital interfaces such as Channel Associated Signaling also use versions of E&M signaling. E&M is considered an obsolete technology for new installations, which generally use Basic Rate (BRI) or Primary Rate (PRI) digital interfaces.

Read more about E And M Signaling:  Signaling Units and Trunk Circuits, Variants, Number of Wires, Address Signaling, Origin of "E&M"