
Theory of Operation
166 025-9035AA
TELCO Signal Descriptions
The interface signals between the telephone switching system and the Model 2200 and
2100 are used for different purposes on different types of telco circuits. The following
charts describe the signals used for each telephone equipment type.
Central Office DID (Selector Level)
Central Office End-to-End
Note Flowcharts for Alpha, Group, Voice Prompts, and PageSaver
tm
are
described in the Operating and Programming Manual (025-9034).
Signal Name Purpose
RING Paired with TIP signal
Carries loop current for circuit supervision and balanced audio
TIP Paired with RING signal
Carries loop current for circuit supervision and balanced audio
ENot used
MNot used
Chassis GND Protective earth ground
Signal Name Purpose
RING Paired with TIP signal
Carries 105VAC ringing voltage, loop current for circuit supervision,
and balanced audio
TIP Paired with RING signal
Carries 105VAC ringing voltage, loop current for circuit supervision,
and balanced audio
ENot used
MNot used
Chassis GND Protective earth ground
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