HP 98568A Installation Instruction page 166

HP 98642A 4-Channel Multiplexer Interface
b. Remove the 4-Channel Multiplexer Interface from its envelope, being
careful to handle the card only by its edges and metal end plate. The
card may be easily damaged by electrostatic discharge (static zap).
c. Place the card on the envelope.
2. Set the Select Code.
SKIP?
If this is the first (or only) 4-Channel Multiplexer Interface you
are installing, you can skip to step 3. The select code is preset
to 13 and need not be changed.
a. Find the group of eight switches on the interface by referring to
Figure 5-29. Switches 4 thru 8 in this group determine the select code.
b. Set these switches to one of the five select codes given in Figure 5-30,
unless you have used them elsewhere (check the Select Code Record on
the Chapter 5, "Interface Cards" tab to see which ones you have used).
Refer to the installation note that came with the interface if you need
additional switch settings.
5-70 Adding Interface Cards