Description of the problem

Huawei OSN1500 equipment uses the N2AT6 single board to interface with the switch to open the signaling service, 1E1M mode, Bell Class I signaling. Using a multimeter to test the switch port voltage is stabilized at -48V, and the AT6 outgoing port voltage gradually decreases from -48V to -43V in steps of a few volts, and the voltage has been unstable, changing back and forth, but the service is normal.

Processing

1, check the multimeter gear selection is correct, positive and negative poles are not reversed;

2、Multimeter test switch port voltage is normal, rule out the possibility of multimeter failure;

3、Check the connection relationship between the multimeter and E&M port, the negative pole is connected to the E&M port, and the positive pole is connected to the PGND end of the device. After confirming that there is no reference relationship between the voltage between PGND and E&M port, correct the wiring: the negative pole is connected to the E&M port, the positive pole is connected to the BGND end of the power box, and a stable -48V voltage is tested.

Root cause

There is no reference to the voltage between PGND and E&M port, the negative terminal is connected to the E&M port and the positive terminal is connected to the BGND terminal of the power supply box, which tests a stable -48V.

Solution

There is something wrong with the test method, check the connection relationship between multimeter and E&M port, negative pole connects to E&M port, positive pole connects to PGND terminal of the device. there is no reference relationship between the voltage between PGND and E&M port, correct the wiring: negative pole connects to E&M port, positive pole connects to BGND terminal of the power supply box, and test a stable -48V voltage.

Suggestion and Summary

In the E&M mode of the Huawei OSN1500 device N2AT6 single board, there is no reference relationship between the port and the PGND of the device itself, and the stable voltage cannot be measured. The voltage between the E&M port and the power box BGND should be tested.

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