PRACTICE 553-2201-184
4.06 Terminal Answers. SSD in SL-1 set sends off-hook signaling to
line
(1)
(2)
(3)
(4)
(5)
circuit on signaling pair.
Off-hook signaling data on data input bus during time slot
0
(via
multiplex control and buffer).
CE detects signaling.
CE changes visual signaling on data output bus during time slot 0.
Visual signaling is applied to
SL-1
set on signaling pair. Line lamp
of SL-1 set changes from flashing to steady light,
CE removes audible signaling from data output bus during message
time
slot (message time slot now assigned for voice
communications).
Audible signaling at SL-1 set stops.
4.07 Talking Connection. PCM codec is enabled during message time
slot.
(1) Digital voice on data output bus is applied to SL-1 set via
multiplex control, PCM codec, digital-to-analog filter, hybrid
._
transformer, and audio pair.
(2)
Analog voice from SL-1 set is applied to data input bus via audio
pair, hybrid transformer, analog-to-digital filter, PCM codec,
multiplex control, and buffer.
4.08 Terminating the Call. Assume SL-1 is put on-hook first.
(1)
SSD transmits on-hook message to line circuit.
(2) On-hook message transmitted to CE through data input bus during
time slot 0 at a rate of 64K bit/s.
(3)
CE detects a change in signaling.
(4) Signaling on data output bus changes; SL-1 set line lamp
extinguishes.
(5)
ADD inputs are removed (no signaling for line circuit 0).
(6)
Enable inputs are removed (message time slot no longer is assigned
to line circuit
0).
CLASS-OF-SERVICE
AND FEATURES
(7)
Circuitry in IDLE condition: ready for next call.
4.09 All calls originating from and terminating on stations connected to
line and trunk circuits may be controlled with or without attendant
assistance. Call restrictions to the exchange network and special services,
are assigned through unique station/line circuit data blocks contained in
the system memory. Similarly, feature assignments are arranged through
the same data blocks. Refer to
553-2YYl-105
for a complete list and
description of features and services. Refer to
553-2YYl-310
for a
description of how features and services are created in the system
memory.
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