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Page 112 of 136
Application
Loop start operation
Ground start operation
Direct Inward Dial operation
553-3121-100
Standard 2.0
Chapter 11 — NTMW07 Trunk/Line Card
The optional applications, features, and signaling arrangements for each
trunk are assigned through route and trunk data blocks.
Loop start operation is configured in software. When the Universal Trunk is
idle, it provides a high impedance toward the CO for isolation and AC
detection. The alerting signal is 20 Hz ringing sent by North American CO.
When an incoming call is answered, ringing is tripped when the trunk places
a low resistance DC loop towards the CO.
For outgoing calls from a telephone set or attendant console, software sends
an outgoing seizure message to place a low resistance loop across the Tip and
Ring leads towards the CO. When the CO is ready to receive digits, it returns
dial tone. The outward address signaling is applied from the system in the
form of DTMF tones or dial pulses.
Ground start operation is configured in software. In an idle state, the Tip
conductor from the CO is open and a high resistance negative battery is
present on the Tip of the trunk. This biases the Tip ground detector OFF until
the CO places ground on the Tip at seizure. After the Tip ground is detected,
the NTMW07 Trunk/Line Card scans for a ringing detection signal before
presenting the call to an attendant and tripping the ringing. A low resistance
is placed across the Tip and Ring conductors and a speech path is established.
An incoming call from the CO places a low resistance loop across the Tip and
Ring leads. Dial pulses or DTMF signals are then presented from the CO.
When the call is presented and the terminating party answers, the NTMW07
Trunk/Line Card reverses battery and ground on the Tip and Ring leads to the
CO. The trunk is arranged for first party release. The CO releases the trunk
by removing the low resistance loop and normal battery and ground are
restored at the system.
September 1998
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