UX-258TH

FO-475TH

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description

1) Block diagram

TEL/LIU PWB

 

 

 

CONTROL PWB

 

 

HS

CML

GAIN-C

TXCONT

TEL LINE

 

H

TXOUT

 

HS DETECTOR

L

 

 

 

 

 

EXT

 

CI DETECTOR

 

0

 

 

 

 

 

 

RXIN

1

 

 

 

 

1

HANDSET

 

 

 

0

 

 

 

TELIN

 

 

 

 

TELOUT

 

 

 

 

 

VOL A

 

 

 

 

VOL B

 

 

 

 

VOL C

HOOK SW

 

 

SP AMP

 

 

 

 

 

 

 

 

4051

 

 

 

SPEAKER

 

 

TEL MUTE

CI

RHS

+5V

+24

DG

1

 

0

 

1

0

BZCONT

 

0

 

1

 

4053

1

0

SIGTX

SIGRX

TXCONT

RXCONT

MONITOR

BZCONT

RCVOL

SP MUTE

TEL MUTE

CI

MODEM

(R96V24)

FC200

GAIN-C

CML

HS

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

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Sharp UX-258TH Circuit description of TEL/LIU PWB, TEL/LIU block operational description, Block diagram, Block description