Epson TM-U375 Technical Manual page 52

CONFIDENTIAL
Operation panel section and cover open detection
circuit
The operation panel section includes four LEDs (POWER,
ERROR, JOURNAL OUT, and VALIDATION/SLIP), two
switches (PAPER FEED and RELEASE) and a photosensor
(for detecting whether the printer cover is open or closed).
These are mounted on the switch circuit board unit and
sensor circuit board set, which is connected to the main
circuit board unit via a connector (CN8). Driving of the
LEDs and detection of the switches and photosensor is
controlled by the CPU (U12), and signal input/output is
conducted through the gate array (U19) ports.
Figure 2-42. Operation Panel Section and Cover Open Detection Circuit
2-21