Nortel Meridian 1 Manual page 38

Intelligent peripheral equipment circuit cards for New Zealand
Dialling
The central office sends address information in the form of loop disconnect
signalling or dual tone multifrequency (DTMF) digits.
Loop disconnect signalling
Loop disconnect pulses are detected at speeds of up to 22 pulses per second.
The minimum interdigit pause is 230 milliseconds. Inverted dialling, rather
than conventional dialling, is supported in New Zealand. (Inverted dialling
is described in the Features description section that follows).
DTMF signalling
DTMF signalling is used with the NT5K48AA Extended Tone Detector Card.
When the NT5K17BA DDI card receives DTMF tones from the central
office, it passes them directly to the NT5K48AA XTD card. The following
frequencies are used:
Table 24
DTMF digits
Low Group (Hz)
697
770
852
941
Answer
When the terminating party answers, the DDI unit reverses battery and
ground on the tip and ring leads (-48V on Tip and Ground on Ring) and
establishes a speech path.
Far End Release
The central office disconnects the call by presenting a high impedance loop
of 9K ohms or greater in the direction of the DDI unit.
Direct Dial Inward trunk card
High Group (Hz)
1209 1336
1 2
4 5
7 8
* 0
Option 11 - Description and Instal-
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3 A
6 B
9 C
# D