AT&T 3B2 Maintenance Reference Manual page 143

Power Supply
The shielded power supply occupies the left rear corner of the cabinet. Model-specific
information about power supplies follows.
Model 300/31 O
Version 2
A bundle of 23 wires from the power supply divides into three destination cable-connector
assemblies that connect to the system board, floppy drive, and hard disk drive. Pinouts for the
cables are given in Table 6-1. The connectors for the disk drives are of the same type for both
units.
NOTE: Two Model 300 and 310 power supplies are available, one supplying 20 A maximum
and the other 22.5 A maximum. They are easily differentiated by the color of the power
switch (red on the 20 A and black on the 22.5 A). The larger capacity power supply may be
needed when using the intelligent serial controller (ISC) cards. This is because of the higher
power consumption of the ISC card versus other
1/0
feature cards. Table 6-2 shows which
power supply is needed for all configurations with ISC cards.
382 Subassemblies 6-3