Nortel TFC002 Manual page 26

Page 18 of 64 Equipment specification and operation
553-2681-100 Standard 5.00
Outgoing seizure
Upon seizure of the RLT by the Remote site, the RLT provides ground on the
tip lead and a battery on the ring lead, and it waits 256 ms.
If the DC resistance across the tip and ring leads is greater than 20-K Ω, the
site provides steady ringing superimposed with –48-V battery through up to
220 Ω of resistance on the ring lead.
If the DC resistance across the tip and ring leads is less than 1300 Ω, then the
CO trunk at the Main site has not released from a previous call, and the RLT
is locked out until the Main site removes the loop. A trunk-error message
(TRK 241) is printed and another RLT circuit is used.
The ringing supply at the Remote site should generate AC ringing voltage
between 75- and 100-V rms at a frequency of 20 Hz (±3 Hz).
Detecting answer supervision
The RLT detects a decrease in DC resistance across the tip and ring leads
from at least 20-K Ω to 1300 Ω or less as an off hook signal from the Main
site equipment. If the off hook signal persists for at least 256 ms, the signal is
an answer supervision. The RLT trips ringing within 100 ms when it detects
the answer signal. Ringing can be tripped during both the silent and ringing
intervals.
Talking state
After answer and until disconnect, the RLT provides ground through a
maximum of 425 Ω of resistance on the tip lead and –48-V battery through
up to 425 Ω of resistance on the ring lead.
Flash signal
The CAS attendant at the Main site controls the RLT by the console signal
Remote (SIG REM) key or the release destination (RLS DEST) key. The
operation of this key sends a timed flash signal to the RLT. The CAS
attendant is required to control the RLT functions by flashing to request a
Digitone receiver for the calling party and cancellation of a prior attendant
request (Release Destination).
August 1996