Epson Equity 286 PLUS - Manual (Page 152)

Note
If the package containing your disk drive came with
instructions for folding the cable before you install it in
the computer, you can ignore the instructions. No special
folding procedure is necessary.
The connector at one end of the cable has two rows of
holes, one of which is blocked with a plug, as shown below.
The ribbon cable socket on the back of the drive has two
rows of pins. In one of the rows, a pin is missing.
ribbon cable connector
ribbon cable socket
Installing and Removing Disk Drives
B-13