Citizen CT-S310II User Manual page 17

Rear connectors
AC inlet
USB cable clamp
Interface connector (USB, serial)
Cash drawer kick-out connector
Interface connector (USB, serial)
Connects to the interface cable (USB, serial).
Cash drawer kick-out connector
Connects to the cable from the cash drawer.
AC inlet
Connects to the AC power cord.
USB cable clamp
Fixes the USB cable in place to prevent it from being pulled out.
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