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Basic Troubleshooting and Repair
Ear & Mouth (E&M) Trunk
You use the E&M trunk in Tie Trunk applications. The E&M trunks support
all the signaling information.
The Tip-Ring is used in a 2-wire operation shown in Figure 26, “E&M Trunk
- Type (2-wire),” on page 260.
The Tip-Ring and Tip Rx-Ring Rx is used in a 4-wire operation shown in
Figure 13 - E&M Trunk - Type V (4-wire).
Type I
Type 1 is used in applications when a telephone company is providing a
transmission path between PBXs. The E&M circuits connect to Telco-
provided Signaling circuits, which prepare the E&M signals for long
distance use.
Each end is identical to the other; all required voltage translation is
provided by the cable carrier.
Note: Type 1 may be used in a 2-or 4-wire operation.