Nortel Networks Video Gaming Accessories 553-3001-211 Manual De Usuario

 NT1R20 Off-Premise Station Analog Line card

Incoming calls to a telephone connected to the NT1R20 OPS analog line card 
originate from stations that can be local (served by the 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 toward the OPS analog line card. (see 
Table 67).

Line card unit idle

Group on tip, battery on ring
High resistance loop

No battery current drawn.

Far-end station goes off-hook and 
addresses (dials-up) the near-end 
station. The system receives the 
incoming call on a trunk and determine 
the TN.

Incoming call

Ringing

The system applies 20 Hz ringing to ring 
lead.

Near-end station 
off-hook

Low resistance loop

Two-way voice 
connection

The system detects increase in loop 
current, tips ringing, and put call through 
to near-end station.

Near end station 
hangs up first

High-resistance loop

If near end station hangs-up first, the 
line card detects the drop in loop 
current. 

Line card unit idle

Group on tip, battery on ring
High resistance loop

Line card unit is ready for the next call.