Panasonic KX-FP101AL Service Manual page 148

KX-FP101AL
3. [Cover Open Sensor (PS303)]
When the operation panel cover is closed, the shelter plate is lifted, the phototransistor becomes ON, and the input signal of
IC301-20 pin (Operation) becomes a low level. When the cover is opened, the shelter plate shuts the sensor light, the
phototransistor becomes OFF, and the input signal of IC301-20 pin (Operation) becomes a high level.
4. [Hook Switch (SW401)]
When the handset is lifted, the switch turns ON, and the signal at pin 21 of IC301 becomes low.
When the handset is returned, the switch turns OFF, and the signal at pin 21 of IC301 becomes high.
Open
Closed
ON-Hook
OFF-Hook
Operation Board
Phototransistor Signal (IC301-20 pin)
OFF
ON
Operation Board
SW Signal (IC301-21 pin)
OFF
ON
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High level
Low level
High level
Low level