Panasonic KX-F1200 Service Manual And Technical Manual page 125

[ KX-F1200
b. NCU SECTION
6-1. GENERAL
This section is the interface with the telephone line and external telephone. It is composed of remote FAX activation circuit,
bell detection circuit, pulse dial circuit, auto disconnect circuit, line amplifier and sidetone circuits and multiplexer.
6-2. REMOTE FAX ACTIVATION CIRCUIT
1) Circuit Operation
After detecting the bell signal, another telephone connected to same line activate the set to FAX mode by using DTMF signal.
Line l/Line 2 --* RLY 1 -* T4 -* IC8 (15 --* 2) ---*C76 --* R92 --, IC22 (2 --* 1) --* R113 --* Q22 (C --, E) --* IC7 (15/11 -* 13)
--* CN1 (2) --* Modem
6-3. BELL DETECTION CIRCUIT
1) Circuit Operation (ex. Line1)
Signal waveform of each section are indicated below. Signal (low level section) input to pin 76 of gate array ICl are read out
at CPU and judged as bell.
Between Tip and Ring (Line1)
about150V
Between PC1(1) and (2)
,.,vov
1°5V
PCl(4)/Gate Array IC1 (76)
(Line1)
Tip-* L1 -* C1 --* PC1(2 --* 1) -* R1 --, L2--, Ring
'_Line2 is the same as above.
6-4. PULSE DIAL CIRCUIT
1) Circuit Operation (ex. Line1)
In OFF-HOOK Condition, the photocoupler PC2 pin (2) is low level by IC1 pin (98) and PC2 pin (4) is low level so Q1 is ON.
At the time of pulse dial operation, PC2 pin (2) becomes high level by IC1 pin (98), so that PC2 pin (4) becomes high level,
and Q1 becomes OFF line ON/OFF by high/low control for ICt pin (98) makes pulse dial operation possible.
IC1 (98) High Level --* PC2 (2) High level --, PC2 (4) High Level --, Qt OFF --* Telephone Line (Line1)
._ Line2 is the same.
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