HP 3000 SERIES II System Service Manual page 85

Maintenance Panel Operating Procedures
The bistable switches, shown in the down position, will illuminate the lamp/lamps indicated by the
numbers above the switch when the switch is placed up. The two-position spring return switches, shown
in the up position, will extinguish the lamps indicated by the numbers below the switch when the switch
is held down. The three-position spring return switches (REGISTER SELECTION switches) have a code
above and below the switch that will be displayed when the switch is held in that position. Stenciling on
the panel has not been shown for clarity. Where two pairs of numbers are present, two lamps will be
illuminated. For example, 1,8 and 9,8 signify that group 1 lamp 8 and group 9 lamp 8 will be illuminated
when the switch is exercised, the lamps will extinguish when the switch is off. The reverse condition
applies to the two-position spring return switches, extinguishing the lamps when the switch is exercised.
When exercising the REGISTER SELECTION switches, a binary coded value is presented by the lamps
in group five. The coded value appears twice, in bits 0-5 and bits 8-13. The indications presented by bits
8-13 should be ignored.
CAUTION
After the switch test is complete, be sure all bistable switches on the
Maintenance Panel are in the down position before restoring S1 on the
MPI PCA to the NORMAL position. This will prevent information
from entering the computer when the switch is returned to NORMAL.
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