atcomsystems.ca/forum Forums General General Telephone & Systems Information 60Hz buzz on ISDN

Long version: https://www.dslretorts.com/Paladin/archives/002365.html

I've killed the lights around it, no change. Moving the phone several feet does not change the noise. Running on rack mount NT1/power in the Telephone room or stand-alone NT1/power in the client's office makes no difference. Cat-5 4-pair or Cat-3 25 pair via different conduit runs -- no difference. Maybe I should try a third new phone?

I would call electrician to check out on good electrical ground.

Mike, this is just theory as I know little about ISDN phones. Since in theory you can only have AC power induction on the analog portion of a circuit and the phones are digital, have you tried putting a choke on the handset cord?

If I understand correctly you say on the other site that plugging it in at the phone room you have no noise. The other suggestion I would have is have someone start killing breakers as you listen to see if you can determine the source of the induction.

I know little about ISDN also but can you swap the phone with one from one of the other offices to see what effect that might have?

This has to be induced into the analog circuitry of the phone by something local. The digital ISDN wiring to the phone wouldn't cause it.

-Hal

The grounds are very good. When we replaced the phone it was like for like, a Lucent i2021. When I used a Fijitsu I had no noise. Unfortunately the client prefers a noisy Lucent over a quiet Fijitsu.

No one knows much about ISDN -- it is not common enough. Plus the advantage of ISDN is that it has a kadzillion options so it can be configured to do anything. The disadvantage is that it as a kadzillion options that can be configured wrong. Since the problem started when the line was moved *and* they built a new O.E. I'm blaming the options in the office until proven otherwise. I'd have to get a key to her office and come in on my own time on a Sunday to run around killing power.

Mike,
Would it be benifical to take a full charged UPS and connect it to her phone? Pull the AC power feeding the UPS and see if the hum appears on the phone? That may give you an indication if the AC wiring is a problem.

-Larry

I can’t think of any provisioning option for an ISDN line that would cause a 60-cycle hum, at least not in a 5ESS. Usually if the provisioning is wrong the circuit won’t work. In the older 5ESS switches each ISDN used a separate line card. It could be the line card itself. I’m like you. I look for what is different or changed. The new OE would be suspect to me.

There is an option in the 5ESS for National or Custom (5ESS) ISDN. If memory serves me as correct, if this option was wrong, the circuit would not work at all. If you have the ability to switch between National & Customer on the telephone, you may want to try it. I don’t think this is the issue but it’s worth a shot.

You did mention that you had the noise with the Lucent set but not with the Fujitsu and that you’re in a new building. This would make me think that maybe something is different in the new location that is causing the hum in the Lucent set.

New building, metal frame? Frame not grounded adequately. 1 GIANT 60 htz transmitter! I've seen it 1 time in 27 years in this @#$%%^^&*() business! But it was an old building that had an upgrade of electrical system and took 2 months to find the (literally) loose bolt! And of course the power was grounded properly! At the power transformer on the other side of the parking lot! Thank GOD I had an electrician that knew something besides friday is payday and never connect black to white except in a switch loop. John C.

This is really weird. It seems like it would be some sort of grounding issue. I like bf6b5yr's point that it may possibly be a faulty OE. I've been able to resolve similar weird symptoms simply by a running standard DSL and CPE tests on the affected circuit. The 5ESS DSL and CPE tests are great for automatically resolving weird glitches and 'buzzes'. If the tests were successful for the D and two B channels, and the symptom still existed, I would then try reassigning the ISDN circuit over to a different OE.

bf6b5yr, Our 'AIU' ISDN line packs support up to 16 circuits per pack.