Nortel TFC002 Manual page 28

Page 20 of 64 Equipment specification and operation
553-2681-100 Standard 5.00
Incoming seizure
The CO trunk at the Main site detects seizure by an RLT at a Remote site
when the RLT simultaneously provides
— a ground through 1.2-K Ω of resistance or less on the tip lead
— ringing with superimposed –48-V battery on the ring lead through a
resistance of 1.2-K Ω or less
The maximum delay of ringing must be less than 5 seconds after ground and
battery detection, and the ringing must last more than 640 ms. If any one of
the preceding conditions is not satisfied, the call is not presented to the CAS
attendant.
Disconnect before the attendant answers
Before the attendant answers the call, tone ringing should be 2 seconds on and
4 seconds off. If there is no ringing for longer than a programmable timer, the
call is withdrawn from presentation to the attendant.
The CAS attendant answers
When the CAS attendant answers, a resistance of 800 Ω or less is applied
across the tip and ring conductors at the CO trunk. A two-way transmission
path between the RLT and the CAS attendant is established within 160 ms to
avoid clipping initial speech. The circuit maintains the low resistance across
the tip and ring leads until the RLT is flashed or disconnected by the
attendant.
August 1996