Figure 2.9 Block Diagram Of The C.o Line Interface Circuit - Samsung OFFICESERV 7100 Service Manual

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2.5.3.2 Major features
The major features of the 8TRK module is as follows:
Structure
The following figure shows the block diagram of the C.O line interface circuit:
Tip
Relay
Protection
Loop
Line
Ring
Port control circuit
(Relay Drive Circuit)
Dial Pulse Generation
Circuit
The above circuit consists of DC current by-pass circuit, matching trans, balance network, hybrid
circuit, channel assign timing control, PCM CODEC, digital gain circuit logic to transmit/receive
voice frequency(300~3400 Hz) to/from the C.O. line. In addition, it constructs a separate DC by-
pass circuit to miniaturize a transformer for voice path.
This circuit embeds the HOS and Ring Signal Detection circuits and uses the TSAC Enable
signal generated inside TMC to control the highway buffer(74ABT125) of the time slot
assign circuit. The Hybrid circuit for impedance matching is designed as the Hybrid circuit
for the line impedance of 600Ω .
Voice Sending/Receiving Part
This part performs the surge protection function via the primary protection to withstand the
high voltage supplied between tip lead and ring lead. In addition, the part constructs the
tertiary protection circuit by using a zener diode inside the impedance matching circuit on
the transformer secondary side. The bi-directional voice received from the C.O board is
separated from the line loop feeding power and entered to the voices signal transformer
through the coupling capacitor.
2-16
Rectifier
&
DC By-pass
Conversion
4W to 2W
Ring Loop
Detection Detection
Time Slot
Assignment
Port
Status
Read
Automatic Gain
Circuit
Controller(A.G.C)
TMC(STL7053)

Figure 2.9 Block Diagram of the C.O Line Interface Circuit

Hybrid Low
Base
Balance Pass
Gain
Circuit Filter
Impedance Low
Setup
Matching Pass
Circuit
Circuit Filter
Data & Address Bus
Control Bus
Buffer
Circuit
Highway Signal
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