Operation Board Section - Panasonic KX-FHD332C Service Manual

A bell is received at EXT. TAM and EXT. TAM is connected to the
line, making a DC LOOP. Then, PC105 detects this voltage. During
detection, PC105 (4) becomes low.
(DC LOOP)
Tip L102
L104 RLY101(5, 3)
2. CNG/VOX signal detection circuit
The CNG signal from the other party's FAX is detected in MODEM
IC505 (digital board).
(Signal path)
Refer to CHECK SHEET
3. Remote receiving
This is the parallel-connected DTMF signal for the TEL or EXT.TEL
mode between T and R. When the other party is a FAX, the unit
switches to FAX receiving.
(Signal Path)
Detects the DTMF signal in the MODEM.

7.12. OPERATION BOARD SECTION

The unit consists of a LCD (Liquid crystal display), KEYs and LEDs (light-emitting diodes). They
are controlled by the Gate Array (IC301) and ASIC (IC501: on the DIGITAL BOARD).
The key matrix table is shown below.
Key Matrix
LED
Caller IQ LED ON/OFF port.....LED2 (IC301-36)
PC105 (2, 1)
L103
().
L105 Tip1
POS101 Ring
191
(EXT.TAM) Ring 1