Nortel Meridian 1 Manual page 14

NT5K93 Central office trunk circuit card Page 9 of 44
Call placed by central office
Fastguard signal
Before applying ringing to the Option 11, the central office sends a Fastguard
signal (battery reversal) that is used to busy a trunk circuit against outgoing
calls. The NT5K18BA trunk card, however, can not detect battery reversal
in the idle state.
Ringing
The central office applies ringing to the ring wire and -50V dc to the tip wire.
The Option 11 ringing detector trips to indicate an incoming call.
Answer
The Option 11 answers the call by placing a loop between the tip and ring
leads. The central office responds by removing the ringing and reversing
battery on the tip and ring leads.
Central office disconnect
The central office sends a disconnect signal by returning to the polarity of the
idle state and removing the potential from the tip lead. The Meridian 1
responds by removing the dc loop between the tip and ring leads.
Option 11 disconnect
The Option 11 disconnects the call by removing the dc loop between the tip
and ring leads. The central office responds by returning to the polarity of the
idle state and removing the potential from the tip lead.
Loop start operation
Loop start operation is configured in software and is implemented in the card
through software download messages.
Idle state
In the idle state, a ringing detector is connected across the tip and ring leads.
The capacitance between the tip and ring leads is 1.8 µF with a resistance
greater than 5 kΩ. The central office applies -50V to the ring wire and
ground to the tip wire.
Call placed by Option 11
To place a call, the Option 11 places a low resistance loop across the tip and
ring leads.
Intelligent peripheral equipment circuit cards for New Zealand Option 11 - Description and Instal-