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Humming noise with Mitel 7187a analogue phone

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doktor

doktor

IS-IT--Management
Dec 3, 2003
3,841
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DK
Dear Sirs
If you use your analogue phone Mitel/Aastra 7187A and a headset is connected in the headset port, - and the headset is charging - the user will hear humming noise in the analogue phones handset.

We have tried to install ferrite cores on all cables - between the PBX and the analogue phone Mitel 7187A, the cable between the phone and headset and the power cable.
All this w/o success.

Our customer has also many Aastra/Mitel 4187A analgue phones and these phones do NOT have this problem.
The Wireless headsets used are Jabra 9120 and 9450 and Sennheiser.

We have tried to swap the cords towards the PBX (-48V and 0V). But no change here.
The idea, we have currently is to insert a 10 nF capacitor in the analogue phones handset in parallel with the speaker??

Maybe you have some hints.
Let me know your opinion.

BR doktor

///doktor
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Your post is unclear. Is this hum prevalent on ALL phones with headset plugged in? Are the handsets plugged into the phone or the headset amp?

Marv ccna

 
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Asstra 7187A:
Jabra 9120 not supported
Jabra 9450 4 flavors supported

Aastra 4187A:
Jabra 9120 not supported
Jabra 9450 3 flavors supported

Sennheiser:
No model given by you

You may have some interference from other devices or power bars at the station/cubical/office.
Find a working combo then move them both to a station/cubical/office that has an issue to help troubleshoot.

You may need to try an RFI Filter for the handsets on the 7187a's


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Toronto, CAN
 
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Hi Again

Thank you for your fast replies.

We see the issue only when the Wireless headset is charging in the charger/bay.
If the user chooses to use the Mitel 7187 phones handset, then he/she will hear the humming noise.
The user will not hear any noise when using the headset.
We do not have this issue with the elder analogue phone type Mitel/Aastra 4187.

Ferrite cores have been tried on all cables, w/o luck.

BR Henrik

///doktor
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Update:

Is this hum prevalent on ALL phones with headset plugged in?
Yes, hum is heard in the handset, if the Wireless headset is charging.
On all 7187 phnones, NOT on the 4187 model.

Are the handsets plugged into the phone or the headset amp?
The headsets are Wireless and the bay/charging station is connected to the 7187 phones special headset connector.


///doktor
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You did not really answer the question but will assume "the handset is plugged into the phone as normal"

Do not confuse Ferrite coils with RFI Filters.


A crackle or buzzing sound – try moving your headset base about 30cm away from your telephone (radio transmission may be too close) This includes things like radios, stereos, ipods or any other electrical transmitting items. They should not be in the room if you are using a telephone headset and get interference.

As I said above test a non working combo in place of a working combo to test this theory.

Have you called the manufactures support line yet?

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Hi Curlycord

Yes, "the handset is plugged into the phone as normal".
So both handset - connected to the handset interface of the analogue phone and the Wireless headset are simultaneously connected.
I will test with a longer cable, but I guess that that work-around will not be acceptable.

Can you recommend a RFI filter or should we try with a capacitor over the handset-speaker?

I have contacted the different Companies involved in this matter.

BR Henrik

///doktor
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I only know Plantronics makes one, I have no experience due to never having your issue.

Using a longer cable and also trying to swap the combo's will narrow down the issue but if both headsets have issue with the same model phone then you would think the model phone is the culprit.



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Hi there

The idea, we have currently is to insert a 10 nF capacitor in the analogue phones handset in parallel with the speaker.
Maybe that could help?

///doktor
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In the sound business, when we have a hum, it's usually due to a ground fault.

Might try a different circuit for charging the headset. Just a thought.



Just my $.02

"What the captain doesn't realize is that we've secretly replaced his Dilithium Crystals with new Folger's Crystals."

--Greg
 
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Have you tried connecting the headset amp to the handset port of the phone and connecting the handset to the handset port on the headset amp?

Marv ccna

 
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Marv please record and say that 10 times really fast and then post the link to the wav file here when done.
Thanks

I also had ground in mind but so many users having same issue but doktor really needs to do the stated tests above and report back the findings.

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Dear Sirs

We have tried this:
"Have you tried connecting the headset amp to the handset port of the phone and connecting the handset to the handset port on the headset amp? "

But sorry to say -> w/o luck.

Any ideas about the capacitors value? 10 nF or 100nF or?

We tried different grounding an even let the analogue phone run through an ATA box (analogue-to-LAN) box , also w/o luck.

Sorry to say...

///doktor
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Find a working combo then move them both to a station/cubical/office that has an issue to help troubleshoot."
You have not answered this.

What I mean is swap the phone, the headset and the charger with another person/location (that has a working setup) as a test and see if the issue follows.


"I have contacted the different Companies involved in this matter."
And what was the suggested solutions?
Did they both agree they are compatible with each other?

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Hallo.

What I mean is swap the phone, the headset and the charger with another person/location (that has a working setup) as a test and see if the issue follows.
-> this has been tried w/o luck


"I have contacted the different Companies involved in this matter."
And what was the suggested solutions? -> Proposals does not solve my problems with the noise.

Did they both agree they are compatible with each other?
-> The headset and phone are on the white lists.

BR Henrik

///doktor
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Is the problem local to one of the ELU29 boards? In other words, if the extension is moved to a different ELU29, does the problem go away?

Just my $.02

"What the captain doesn't realize is that we've secretly replaced his Dilithium Crystals with new Folger's Crystals."

--Greg
 
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