Nortel Circuit Card Installation Manual page 38

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