Ncu Section - Panasonic KX-F910BX Service Manual

7 NCU Section

7-1. GENERAL
This section is the interface with the telephone line and external telephone. It is composed of EXT. TEL Line relay
(RL101), bell detection circuit, pulse dial circuit, Auto Disconnect circuit, TAM Interface circuit, line amplifier and
sidetone circuits and multiplexer.
7-2. EXT. TEL. line relay (RL101)
(1) Circuit Operation
Normally this relay switches to the external telephone side (break) and it switches to the open side (make) when the set
starts facsimile communication.
IC151 (32) High Level ¤ Q271 ON ¤ RL101 (make)
7-3. BELL DETECTION CIRCUIT
(1) Circuit Operation
Signal waveform of each section are indicated below. Signal (low level section) input to pin 4 of gate array IC151 are
read out at CPU and judged as bell.
Between Tip and Ring
Between PC101(1) and (2)
PC101(4)/Gate Array IC151 (4)
TEL LINE ¤ PC101(1,2-4) ¤ IC151 (4)
7-4. PULSE DIAL CIRCUIT
(1) Circuit Operation
In OFF-HOOK Condition, the photocoupler PC102 pin (2) is low level by IC151 pin (3) and PC102 pin (4) is low level so
Q101 is ON. At the time of pulse dial operation, PC102 pin (2) becomes high level by IC151 pin (3), so that PC4 pin (4)
becomes high level, and Q101 becomes OFF line ON/OFF by high/low control for IC151 pin (3) makes pulse dial opera-
tion possible.
IC151 (3) High Level ¤ PC102 (2) High level ¤ PC102 (4) High Level ¤ Q101 OFF ¤ Telephone Line
48V
| 155 |
KX-F910BX
about 150V
1.5V
0V
1.5V
5V