Avaya Definity SI Maintenance Manual page 1319

DID-TRK (DID Trunk)
Figure 10-24. DID Trunk Interactions
For each call, the CO switch signals the system by opening and closing individual
DID loops (one of the eight ports) and causing the starting or stopping of loop
current.
A DID trunk operation involves three significant aspects:
1. Transmission—deals with the interface requirements regarding all AC
signals. Transmission includes gain, analog to digital encoding, and digital
to analog decoding.
2. Signaling—involves interpretation of DC signals appearing on Tip and Ring
to and from the CO. These signals include off-hook, on-hook, and dial
pulse detection.
3. Switch Connection—involves the connection between the trunk circuitry
and the TDM Bus of the system. It operates the switchhook connection to
the TDM Bus.
Four tests are implemented to diagnose the health of a DID trunk. All of them test
on-board circuitry only. They are:
1. Loop Around and Conference Circuit Test—verifies the transmission
operation of the circuit pack (loop around within the port), and checks the
conference capabilities of all ports.
This test may fail due to noise induced by adjacent electric power lines.
Customers having this problem should resolve it with their local power
company. To temporarily alleviate the alarm caused by the failure of this
test, the test may be disabled from trunk administration Test field. (This
also disables the port diagnostic test).
555-233-123
Switch
DID
Incoming
trunk
calls only
cydff1p1 LJK 030701
Central office
switch
1
2
Issue 4 May 2002 10-533