C-10 SmartSwitch 1800 4.0 User Guide, Rev 01SLT ConnectionsSLT (Single Line Telephone) is a two-wire telephone communication mode. In thismode, the SmartSwitch 1800 presents a telco/PTT interface which looks like astandard telephone set. The SmartSwitch 1800 can be connected to analog stationports (extensions) of a PBX. The SLT option provides the appearance of a two-wiretelephone in a loop-start circuit. An SLT-configured voice port on a SmartSwitch1800 detects ring voltage and closes the loop during off-hook and opens the loop in anon-hook condition.E&M ConnectionsE&M is a communication mode used in PBX-to-PBX communications as shown inthe following illustration.Figure C-5 Inter-PBX TrunkingThis type of interface uses a two-wire or four-wire voice circuit plus up to four wiresfor E&M signaling. In this mode, the SmartSwitch 1800 offers an interconnection pathbetween two PBXs.PBX E&M tie-line connections usually require multi-conductor dedicated circuits tosupport full-duplex voice and separate signaling lines. Typically, eight wires arerequired: four for voice (two wires in each direction) and four for E&M signaling. Afew PBXs use two wires (one pair) for bi-directional voice. The SmartSwitch 1800can interface with either of these circuits.The E&M interface is designed to connect with that of a PBX tie line port, and provideappropriate end-to-end signaling support for a variety of applications. The systemgenerates the "E" signal to the PBX in response to an inbound signal at the remote unit.That signal depends on the application of the remote unit. The local unit will generatethe "E" signal in the following applications:l The remote unit is configured for E&M signaling, and detects an active "M"signal.l The remote unit uses the OPX option, and detects an off hook condition on itstwo-wire loop-start circuit.l The remote unit uses the SLT option, and detects a ring signal on its two-wireloop-start circuit.
