Circuit Description Of Tel/Liu Pwb; Circuit Description Of; Power Supply Pwb - Sharp FO-165 Service Manual

[3] Circuit Description of TEL/LIU PWB

(1) TEL/LIU block operational description
1) Block diagram
CML
SURGE LINE
PROTECTION FILTER
TEL LINE
BLOCK BLOCK
2) Circuit description
The TEL/LIU PWB is composed of the following 12 blocks.
1. Line filter block
2. Cl block
3. Polarity guard block
4. Dial control block
5. Pulse transmitting block
6. ON-hook block
7. Hook detection block
8. Communication circuit block
9. Speaker amplifier block
10. Power supply
11. Sensor block
12. Signal selection
POLARITY
ON-HOOK
GUARD
BLOCK
BLOCK
CI DETECTION
CIRCUIT
DIAL PULSE
SPEECH
GENERATION
CIRCUIT
BLOCK
BLOCK
3) Block description
1. Line filter block
This block is composed of a (L1) and is used to remove noise
from the telephone line.
2. Cl block
This block is composed of a photo coupler (PC3) and is used to
convert ringer signal into a digital signal.
3. Polarity guard block
This block is composed of 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.
4. Dial control block
This block is composed of dialer IC (IC105) and crystal oscillator
(×1). The dialer IC is controlled with 4-bit data from operation
panel when the power is switched off. There is not used the dialer
IC, when the power is switched on.
5 – 8
REC MUTE
RX
HANDSET
TX
TEL MUTE
SIG TX
MPX-A
SIGRX
SPEAKER
AMP
SPEAKER
DOOR/PAPER
SENSOR
LED
HOOK
SW
FO-165A
FO-365A
MODEM
MODEM
CML
CI
SP
PAPS
LED
RHS