3] circuit description of tel/liu pwb, 1) tel/liu block operational description, 1) block diagram 2) circuit description – Sharp FO-475TH User Manual

Page 50: 3) block description

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UX-258TH

FO-475TH

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description

1) Block diagram

2) Circuit description

The TEL/LIU PWB is composed of the following 7 blocks.

1. Speech circuit section

2. Dial transmission section

3. Speaker amplifier section

4. Ringer circuit section

5. Externally connected TEL OFF HOOK detection circuit

6. CI detection circuit

7. Signal/DTMF transmission level & receiving level

Fig. 5

3) Block description

1. Speech circuit section

The receiver volume is an electronic volume type, this model is
switch in 2 steps.

2. Dial transmission section

D.P. transmission: The CML relay is turned on and off for control in
the DP calling system. (Refer to the attached sheet.)

DTM transmission: It is formed in the modem, and is output.

3. Speaker amplifier section

The volume of the ringer sound/speaker sound is controlled with
3-bit signal of VOLA, VOLB and VOLC, and the sound switch is
controlled with BZ CONT.

4. Ringer circuit section

The ringer sound is formed in the tone of 1-chip engine when CI
signal is detected. The amplifier circuit drives the speaker of the
main body.

5 – 8

SIGTX

SIGRX

MODEM

(R96V24)

SP AMP

4051

CI DETECTOR

HS DETECTOR

TEL LINE

EXT

+5V

+24

DG

CI

TEL MUTE

RHS

HOOK SW

HANDSET

SPEAKER

TELIN

TELOUT

RXIN

TXOUT

HS

CML

CONTROL PWB

TEL/LIU PWB

VOL A

VOL B

VOL C

BZCONT

TXCONT

RXCONT

MONITOR

BZCONT

RCVOL

SP MUTE

TEL MUTE

CI

GAIN-C

CML

HS

4053

1

0

1

0

GAIN-C

TXCONT

0

1

1

0

1 0

0

1

FC200

H

L

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