KX-FP320E, KX-FM330E - Panasonic Fax Service Manual Simplified (repair manual). Page 17

17

(Model KX-FP320E/KX-FM330E)

This circuit detects whether the circuit current is flowing or not. It is also used for CPC detection and Ext. Tel Hook
detection.

2. Circuit Operation

If a circuit current of 10 mA or more flows in the IC1 coil when the unit or Ext. Tel is OFF-hook, the IC1 internal sensor
detects this current. Then, depending on the direction of the current, the IC1-5 pin or 6 pin switches to a low level.
Then, Q1 or Q2 is turns off, Q18 turns on, and the Gate Array IC4-43 pin on the digital board switches to a low level. If
the line is cut off, the IC4-43 pin switches to a high level.

This circuit is only incorporated into the products designed for the German market. Products for other markets are
shorted by J33. This low pass filter attenuates the 16-kHz account signal from the commutator to eliminate influence on
the conversation and communications.

2. Circuit Operation

This low pass filter is an eighth-order active filter, and the cutoff frequency is approximately 4 kHz.

RLY1

C3 R7

B

A

EXT.TEL

CN9(2)

(Digital)
IC4 43

Q2

Q1

Q18

R44

Line

A

B

IC1

1 2 5 6

R192

Level

frequency

IC11 

IC11 

IC12 

IC12

C61

C63

C55

C62

C65

C66

C60

C58

R78

R86 R81

R77

R82

R88

R94

R91

J33

R79

C54

dB

0

-48dB/oct

4KHz

RX Signal
input

RX Signal
output

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