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Page 572 of 894 NT8D14 Universal Trunk card
553-3001-211 Standard 2.00 September 2004
Direct inward dial operation
Incoming calls
An incoming call from the CO places a low-resistance loop across the tip and
ring leads. See Figure 120 on page 573 and Figure 121 on page 574.
Dial pulses or DTMF tones are then presented from the CO. When the called
party answers, the universal trunk 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, at which time normal
battery and ground are restored at the near-end. This also applies to incoming
tie trunk calls from a far-end PBX.
Note: The near-end can be configured for immediate start, delay dial, or
wink start.
Two-way, loop dial repeating, TIE trunk operation
Incoming calls
In an incoming call configuration, the far-end initiates a call by placing a
low-resistance loop across the tip and ring leads. See Figure 122 on page 575
and Figure 123 on page 576.
This causes a current to flow through the battery feed resistors in the trunk
circuit. Address signaling is then applied by the far-end in the form of DTMF
tones or dial pulses. When the called party answers, an answer supervision
signal is sent by the software, causing the System to reverse battery and
ground on the tip and ringleads to the far-end. Far-end disconnect is initiated
by opening the loop while the near-end disconnect is initiated by restoring
normal battery and ground. The operation represented in Figure 122 on
page 575 and Figure 123 on page 576 also applies to incoming DID trunk
calls from a CO.
Note: Where no near-end answer supervision is provided, the party at
the far-end hangs up after recognizing near-end call termination.