Epson 4SLC2-50 - Manual (Page 65)

Connecting An Optional Pointing Device
You can connect a PS/2-type mouse or other pointing device to
the
EXT KB port as shown below, Before you can use the mouse or
other pointing device with your applications, you need to install
the special software driver that came with it. See the
documentation supplied with the device for instructions.
Also, before using a pointing device attached to the EXT KB port,
you must enable the PS/2 Mouse Support Option in the
ADVANCED CMOS SETUP portion of the Setup program. See
Chapter 5 for details on using the Setup program.
Connecting an External Keyboard
If you are typing for extended periods of time, you may want to
connect an external keyboard. You must first connect the
mouse/keyboard adapter to the
EXT KB port on the computer.
Then connect the keyboard to the adapter.
4-8 Connecting Optional Devices