AR-FN2 (serv.man10). ARFN2 Service Manual-Circuit Descriptions - Sharp Copying Equipment Service Manual (repair manual). Page 7

ULS1 is the sensor same as the transport entry port sensor (PIS).
The rear side connection with the copier is detected.
The light path is interrupted when connected.
The signal is passed to the CPU (IC9-58 pin) through the noise filter of R6 and C8. 
Logic of the signal inputted to the CPU: Not connected 

®

 H, Connected 

®

 L

R41 is the current limiting resistor of LED. R51 is the sensor load resistor.

ULS2 is the sensor same as the transport entry port sensor (PIS).
The front side connection with the copier is detected.
The light path is interrupted when connected.
The signal is passed to the CPU (IC9-73 pin) through the noise filter of R30 and C29. 
Logic of the signal inputted to the CPU: Not connected 

®

 H, Connected 

®

 L

R106 is the current limiting resistor of LED. R29 is the sensor load resistor. 

UCS is the sensor same as the transport entry port sensor (PIS).
The open/close of the upper cover of the transport path is detected.
The light path is interrupted when cover closed. 
The signal is passed to the CPU (IC9-57 pin) through the noise filter of R3 and C5. 
Logic of the signal inputted to the CPU: Cover open 

®

 H, Cover closed 

®

 L

R42 is the current limiting resistor of LED. R54 is the sensor load resistor. 

Unit lock sensor 1 input circuit

Unit lock sensor 1

(ULS1)

Unit lock sensor 2 input circuit

Unit lock sensor 2
(ULS2)

Upper cover sensor input circuit

Upper cover sensor
(UCS)

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