Circuitdescriptionof Teuliu Pwb - Sharp FO-155 Service Manual

FO-155A
FO-355A
[3] Circuit description of TEULIU PWB
(1) TEVLIU block operational description
1) Blockdiagram
CML
RECMUTE
r
, 1
SURGE
TELLINE
ON-HOOK—
TA% PULSE
POLARITY DIALPULSE
SPEECHf
~ PROTECTION FILTER GUARD —
GENERATION — CIRCUIT
BLOCK
BLOCK
I
":[
HANDSET
BLOCK BLOCK BLOCK
BLOCK
TX
L
TELMUTE
;i:
SIGTX
4 MODEM
MPX.B
Y#-DmF
Cl DETECTION
c1
CIRCUIT
L J
D" I
SPEAKER
SP
AMP
2) Circuitdescription
TheTEULIUPWBis composed of thefollowing10blocks,
1. Cl block
2. Polarityguardblock
3.
Pulse transmitting
block
4. ON-hookblock
5. Hookdetectionblock
6. Speechcircuitblock
7. Speakeramplifierblock
8.
Power supply and bias circuit
9.
Sensorblock
10. Signalselection
SPEAKER
DOOFVPAPER
PAPS
SENSOR
1 1
I
I
3) Blockdescription
1.
Cl block
This blockis composedof a photocoupler(PC1)and is usedto
convertringersignalintoa digitalsignal.
2.
Polarity guard block
This
block is composedof diode
bridge (REC1) and is used to
supply a current and voltage of the same polarity to the telephone
circuit regardless of reversion of polarity in the telephone circuit.
5-8