Circuit Card Descriptions
15. DID TRUNK CARD
Brief Description
15.01 The DID trunk card contains six l-way Direct Inward Dial cir-
cuits. It plugs into the digital peripheral bay. One-Way Direct
inward Dialing (DID) provides for direct access to PABX subscriber
lines from the public telephone network.
15.02 DID trunk cards can be used in any digital peripheral bay high
power (upper) slot. The maximum number of these cards is four
per bay. This provides a maximum of 24 ports per peripheral bay.
15.03 The card is 157.5 mm (6.2 in.) high and 366.4 mm (14.4 in.) long.
Major Components
15.04 Major components in the DID Trunk Card are:
l
Mite1
8962
FilterKodec
(one per trunk circuit)
0
Feed Reversal relay (one per trunk circuit) Alarm LED.
Facilities
15.05 The facilities
provide,d
by each trunk circuit are:
0
Trunk activity LED
0
Line protection
0
2-wire
/
4-wire conversion (external to internal)
0
Analog-to-Digital
/
Digital-to-Analog conversion
(plaw)
0
Immediate, Delay Dial or Wink Start supervision
0
Direct Inward Dialing access to PABX subscriber lines
l
Conformity with the EIA loss level plan for
plaw-compatible
PABXs
in North America.
Operation
15.06 A
.trunk
is idle if the resistance across Tip and Ring is 4000
ohms or more. In idle condition the PABX provides forward
battery feed to the line. The Tip is grounded and the Ring is at -48
Volts.
15.07 The CO initiates a call to the PABX by terminating Tip and Ring.
The supervision circuitry. detects the flow of loop current and
alerts the system software. The PABX signals it is ready to receive
dialing by briefly applying a battery reversal to the line. Ring is
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