Epson Apex 20020 - Manual (Page 124)

The procedure for changing a jumper setting is given first, then
the jumper functions and locations for each card are described
separately. All the instructions assume you have already
removed the cover from the computer.
Changing a Jumper Setting
A jumper setting is determined by the jumper’s position: either
between pin A and the middle pin (position A) or between pin
B and the middle pin (position B). Both positions are shown
below.
To move a jumper from one position to the other, use needle-
nose pliers or tweezers to lift it off the board and gently move it
to the other position. Be careful not to lose the jumper or leave
it out of the computer.
Memory Card Jumpers
The jumpers on the memory card control the following
functions:
Amount of RAM (main memory). If you install a memory
card that needs to use part of the main memory, you may
need to change the jumper settings to disable some of the
main memory on the memory card. Be sure to check your
memory card instructions to see if this is necessary.
EPROM size. You can change the EPROM size jumper if
you install a different size of EPROM.