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New Member

white noise from 7940/7960(not for 7902)

I have a white noise(it's weak but always) from 7940/7960. not for 7902 even they are on the same location. I can verify by,

- press the speaker button and minimize the volume. the noise is loud than dial ton.

- pick the hand-set and press the hook(hang-up), I'm hear the noise even no dial tone.

Looks it's not related to the CCM but IP phone hardware itself. If I test the two-way mike put near the IP phone, generates a big noise by the IP phone.

Any idea why a white noise only from 7940/7960(not for 7902) ?

** ICS7750, CCM 3.3(2)spC, all phones connected to 3550 inline power.



Re: white noise from 7940/7960(not for 7902)

Is the problem on all your 7940/7960 sets or just a selected few? If on just a few I would rule out the cabling by taking the phone and plugging directly into the switch with a short patch cable. If the white noise continues you have ruled out the cable. If it is gone you have a cabling problem. Also you didn't mention what firmware load you are on. You might try going to the new load P00305000400.

New Member

Re: white noise from 7940/7960(not for 7902)

I have 30*(7940/7960) and one 7902 phones.

- all of 7940/7960 happen but not for 7902.

- short patch cable to 3550 switch have same result

- same cable tested to 7940 and 7902. noise from 7940 only.

- The firmware for 5.0(3) and 5.0(4) are same result.


Q1) Pick the hand-set(dial tone) and press the hook(hang-up and no dial tone). still I can hear the white noise. is this related to the phone's firmware or CCM ? I think this noise from IP phone itself. not from CCM or cable.

Q2) Any hardware difference between 7940 and 7902 ? (ex, electromagnetic related).

Q3) Any possibility of environment ? (ex, strong electromagnetic in the building). I tested a two-way mike that hear a big noise if I approach it into the IP phone.