IBM 5155 Manual To Operations page 271

45
You must set a system board switch to reflect
the installation of your second diskette drive.
Study the figure below. There are two types of
switch blocks on the system board: rocker
switch block and slide switch block. Identify the
type of switches on your system board. Set
Switch 7 to the Off position.
Slide Rocker
Switch Switch
Option InstaIlation 4-43