IBM 5155 Manual To Operations page 368

Installation Requirements
The expansion unit comes equipped with a fixed disk
drive, a fixed disk adapter, a power supply, and a
receiver card. An extender card must be installed in
expansion slot 2 of your system unit. A cable connects
to the extender card and the receiver card to complete
the electrical connection between the system unit and
expansion unit. With the extender card installed, the
expansion unit has six expansion slots available where
options may be installed. Space also is provided for the
installation of an additional fixed disk drive.
The expansion unit has only one control -- the Power
switch. Whenever power is to be applied to the IBM
Portable Personal Computer, the Power switch on the
expansion unit must be set to On first. If this is not done,
an error message appears on the display. To recover
from this error condition, set the Power switches on
both the system unit and expansion unit to Off. Then
set the Power switch on the expansion unit to On, then
the Power switch on the system unit.
The BIOS kit ROM module sent with the expansion
unit cannot be used on an mM Portable Personal
Computer. Discard the module.
6 Expansion Unit
January 1984