Nortel Networks 1000 - Manual (Page 129)

Operation 129
Incoming calls to a telephone connected to the OPS analog line card
originate from stations that can be local (served by the Meridian 1 PBX)
or remote (served through the public switched telephone network). The
alerting signal to telephones is 20 Hz (nominal) ringing. When an incoming
call is answered, ringing is tripped as the telephone goes off-hook, placing
a low-resistance DC loop across the tip and ring leads towards the OPS
analog line card (see
Table 54 "Call connection sequence-near-end station
receiving call" (page 128) ).
Outgoing calls
For outgoing calls from a telephone, a line unit is seized when the
telephone goes off-hook, placing a low-resistance loop across the tip and
ring leads towards the NT1R20 OPS analog line card (see
Table 55 "Call
connection sequence-near-end station receiving call" (page 129) ). When
the card detects the low-resistance loop, it prepares to receive digits.
When the system is ready to receive digits, it returns a dial tone. Outward
address signaling is then applied from the telephone in the form of loop
(interrupting) dial pulses or DTMF tones.
Table 55
Call connection sequence-near-end station receiving call
State
Signal / Direction
Far-end / Near-end
Remarks
Line card unit idle Group on tip, battery on ring
High resistance loop No battery current drawn.
Call request Low resistance loop Near-end station goes off-hook. Battery
current is drawn, causing detection of
off-hook state.
Dial Tone Dial tone is applied to the near end station
from the system.
Outpulsing Addressing signals Near-end station dials number (loop
pulsing or DTMF tones).
The system detects start of dialing and
remove dial tone.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.