Instruction manual

Tie Trunks
2-40
Installation, SPM, Maintenance, and Troubleshooting Supplement
Signaling Modes 2
There are two signaling modes:
■ E&M. This is a standard interface. The E&M signaling leads are separate
from the transmission leads, requiring a 3-pair wire interface.
■ Simplex. In Simplex, the two signaling leads are superimposed onto the
analog transmission leads, providing a 2-pair wire interface for connecting
two local systems at minimal cost.
Protected or Unprotected 2
Depending on the type of tie trunk installation, protective resistance may be
installed to protect the circuit from outside interference from high-voltage
transients or voltage fluctuations. In Simplex mode, the circuit always requires
protective resistance. The E&M mode can be either protected or unprotected,
depending upon the location of the distant PBX.
Signaling Types 2
Three different signaling types combine with the signaling modes. Together,
these create the proper signaling format for each system. Signaling types in
each mode are as follows:
■ E&M Mode
— Type 1 Standard. Default factory setting. This setting is used to
connect two systems through local telephone company facilities.
— Type 1 Compatible.This setting connects two systems directly
(without using local telephone company facilities).
■ Type 5 Simplex Mode
— This setting is used on 4-wire (2-pair) circuits.