Nortel Networks Circuit Card - Manual (Page 38)

Page 38 of 906 Overview
553-3001-211 Standard 3.00 August 2005
Figure 4
Typical analog line interface unit block diagram
CODEC
2-wire
to
4-wire
conversion
Line
interface
and
protection
Message
waiting
Variable gain
filters
Impedance
matching
transformer
Balancing Network
Tip
Ring
DS-30X or
SL-1 network
loop
Message
waiting
circuit
–150V dc
553-6153
Message
waiting
Ringing
circuit
Ring voltage
Ringing
Off-hook
detector
Off-hook
Tx PCM
Rx PCM