AT&T System 25 - Manual (Page 241)

MAINTENANCE
Table 4-B lists the test points (-5 V, +5 V, -48 V, and GND) for the power supply.
The test points are located on the upper-right corner at the front of the cabinet.
Table 4-C lists the voltages used by the CPs and symptoms
voltages are missing. This information is useful in diagnosing
power distribution problems.
Table 4-B. Power Supply Test Points
that occur when
power supply or
Test Voltage Remarks
Points Limits
+5 +4.80 +5. 15 The green LED on the power supply
monitors this particular voltage
Ground
4-65