Panasonic KX-FLB852CX Service Manual page 243

7.12.12. PRINT TIMING SENSOR
This sensor detects whether the recording paper is at the printing position.
When the recording paper is detected, the shelter plate lets the sensor light pass.
So the photo-transistor turns on, and input signal of IC604-113pin becomes low level.
When the recording paper is not detected, the shelter plate closes the sensor light.
So the photo-transistor turns off, and input signal of IC604-113pin becomes high level.
7.12.13. DOCUMENT SENSOR
This sensor detects whether a document is set in ADF or not.
When a document is set in ADF, the shelter plate closes the sensor light.
So the photo-transistor turns off, and input signal of IC604-115pin becomes high level.
When a document is not set in ADF, the shelter plate lets the sensor light pass.
So the photo-transistor turns on, and input signal of IC604-115pin becomes low level.
Photo-transistor
Paper exits
No paper
Photo-transistor
document exits
No document
Signal (IC604-113pin)
ON Low level
OFF High level
Signal (IC604-115pin)
OFF High level
ON Low level
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KX-FLB852CX / KX-FLB852CXS