Page 36 of 894 Overview
553-3001-211 Standard 2.00 September 2004

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