Panasonic KX-FHD333BR Service Manual page 137

8.6.4. HOOK SWITCH (SW101)
When the handset is lifted, the switch turns OFF, and the signal at pin 25 of IC501 becomes high.
When the handset is returned, the switch turns ON, and the signal at pin 25 of IC501 becomes low.
ON-Hook
OFF-Hook
8.6.5. PAPER TOP SENSOR (PS501)........................"PAPER JAMMED"
When the recording paper is loaded on the print head, the shelter plate shuts the sensor light, and the photo transistor turns OFF.
The input signal of IC501-19 pin becomes a high level. Usually, the shelter plate is lifted, the photo transistor turns ON, and the
input signal of IC501-19 pin becomes a low level.
Recording paper top
No recording paper
Digital Board
SW Signal (IC501-25 pin)
ON Low level
OFF High level
Photo transistor Signal (IC501-19 pin)
OFF High level
ON Low level
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KX-FHD333BR