ADTRAN 25 manual Maintenance

MAINTENANCE

Emergency Transfer Unit Trouble

If the Emergency Transfer Unit (ETU) will not enter the power failure mode, do the following steps:

1.Unplug the cable bringing the control signal from port 7 or 8 on the CPU/Memory CP to the ETU. This cable terminates in a modular jack that is inserted in a modular plug labeled CPU on the left-hand side of the ETU.

2.If the ETU goes into the power failure mode, the CPU/Memory CP is probably faulty or a wiring problem exists. Plug the cable back in, then reset the CPU/Memory CP by removing and restoring power to the system. If the ETU still does not go into the power failure mode, the CPU/Memory CP must be replaced.

3.If the ETU does not go into the power failure mode after the control cable was unplugged in Step 1, the ETU is faulty and must be replaced.

If the ETU remains in the power failure mode continuously (preventing normal operation of the system), follow these steps:

1.At the ETU, unplug the cable bringing the control signal from the CPU/Memory CP.

2.Using a modular jack breakout box and voltmeter, check to see that 48 volts are present between pins 1 and 2 and pins 3 and 6 of the control cable from the CPU/Memory CP.

3.If the above voltages are present, the ETU is faulty and should be r e p l a c e d .

4.If the above voltages are not present, either the CPU/Memory CP or the cable is faulty and should be replaced.

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