our customer use only 75ohm for E1 port impedance, when we checked the slot configuration in U2000, we found: so in interface used for both PQ1:slot 2 and 3 is D12S for 120ohm
the question is why slot 3 didn't report alarm even it use same interfaces?
1-we checked the boards manufactury of PQ1/slot 2:
so PQ1/slot2 is PQ1A, it means port impedance only for 75ohm.
2-we checked the boards manufactury of PQ1/slot 3
so PQ1/slot3 is PQ1B, it means port impedance only for 120ohm
=> this is why PQ1/slot 2 report the alarm and E1 test fail, because the type is PQ1A and interface used is D12S for 120ohm
for PQ1/slot 3 the type is PQ1B and interface used is D12S=> impedance match and E1 test succeed