EPSON AcuLaser C1900/AcuLaser C900 Revision B
Appendix Connectors and Jumpers on Circuit Boards 224
PJ19 Connector for connection to Optional Cassette Unit
PJ20
⇒ Detection of Intermediate Transfer Belt Unit (PWB-G)
⇒ Belt Location Detection Sensor (PC5)
PJ21
Harness for connection to detection terminals for presence of 
Photoconductor Unit or new Photoconductor Unit
(Connection to the terminals on the back of the Drum Unit Slide Cover)
PJ22 Connector for connection to High Voltage Power Supply Board (HVPS)
PJ23 Connector for connection to Laser Control Board (on PH Unit)
PJ24 ⇒ Polygon Motor (M3)
PJ25 ⇒ Fuser Cooling Fan Motor (M5)
PJ26 ⇒ AIDC Sensor (AIDC)
PJ27 ⇒ Toner Cartridge Detection Sensor (PC8)
PJ28 Socket for EEPROM (IC3)
PJ29 ⇒ Fuser Loop Flapper Solenoid (SL6)
PJ30 (The same circuit that is used for PJ14)
Table 7-5. Engine Board (PWB-A) -- Connectors  (continued)
Connector
Function