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Humming noise with Mitel 7187a analogue phone

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doktor

doktor

IS-IT--Management
Dec 3, 2003
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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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...or are both model phones on the same cards?

Since they are analog why not take the package home or office and test offsite?
If onsite then issue would then be the MX-ONE 5.0 PBX or something on site such as the Florescent lights.

Maybe get a ground tester and test a station as well the PBX receptacle.


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Hi there.

We did some test and her is some:

Additional information:
If we swap the handset and headset interfaces - i.e. put the handset in the headset interface and the headset in the handset interface, the noise disappears.
But then the users still need to use the hedset button when using handset and vice versa.
So we need your help again concerning how to solve this issue.

The PBX is grounded after "the book", so I don't think we have to use more time on that direction.
We also tried with 3 ferrite cores on the power cord for the headset and some ferrite cores for the cable between the phone and the headset base/charger - w/o luck.

So I guess we need to look into the headset interface - to install a capacitor some where to eliminate the noise, Or??

BR Henrik

///doktor
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s the problem local to one of the ELU29 boards? In other words, if the extension is moved to a different ELU29"
You have not answered this, this determines if the phones are not liking these cards when a headset set is connected or cards not grounding.

"Since they are analog why not take the package home or office and test offsite?"
Have you done this yet?
This determines if a Site(ground or objects/lights with interference) and/or PBX issue.
This test must be done.

"he PBX is grounded after "the book"
Did you actually test the ground with tester to make sure it's done right?
Do not just look at it or assume.5

Capacitor
You should not have to install a capacitor, that is the manufactures job otherwise best to ask that question in an electronics forum.

From Jabra:
have set up my GN9120/GN9125 correctly, but I am getting a buzzing sound on my headset.
Your telephone may not be fully immune to the radio transmission between your headset and base. To
overcome this problem, move the base at least 30 cm/12” away from the phone. If you have a European
version, you can instead choose to set the headset to Low Power mode.

Make sure you answer all question and do all tests provided to you above.



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Hi There

Here is our report:

"s the problem local to one of the ELU29 boards? In other words, if the extension is moved to a different ELU29"
You have not answered this, this determines if the phones are not liking these cards when a headset set is connected or cards not grounding.

Answer from doktor: We tried with diffrent ports on different ELU29 and even a direct PSTN line - still the problem with the noise exists.

"Since they are analog why not take the package home or office and test offsite?"
Have you done this yet?

Answer from doktor: We tested this w/o luck.

This determines if a Site(ground or objects/lights with interference) and/or PBX issue.
This test must be done.

Answer from doktor: We can now say that this problem with noise from the Wireless headset - does not come from bad grounding of a PBX.

"he PBX is grounded after "the book"
Did you actually test the ground with tester to make sure it's done right?
Do not just look at it or assume.5

Answer from doktor: Taken notice of this.


Further tests done:

We have tested with other power supplies, but still we have the noise.

We have tried to use different Wireless heasets and used diffrent power supplies, but still we hear the noise.

Recommendations from Jabra (and other headset suppliers) is to use a longer cable between the phone and the headset base/amplifier.
This has been tried without luck - the noise is still there.


We have also tried to add ferrite cores on the PBX line (or PSTN, if used), but this does not remove the noise either.

Workaround:

The only workaround with a bit of succes was to insert the handset cable in the headset connector and vice versa.
But with this workaround the user should use the handset button for the headset and vice versa.


Let me know if you have other ideas.
/Henrik



///doktor
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From Jabra:
"If you have a European
version, you can instead choose to set the headset to Low Power mode."

Aside from that I am Outta Ammo!

And based on the hordes of people chiming in they have never had this issue so guessing their call centers all use digital sets or do not use wireless headsets with this model of phone.

300 sensitive phones, if they were new I would seek a return for another model.




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I suspect you have over loaded the 2.4Ghz spectrum with that many units in one place. I know Plantronics puts in their spec max number of units in any one location and it's not very many ( aprox. 10 if I recall).

Check out this PDF from SenheiserDECT Density

Marv ccna

 
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Wonder if this might help:


Have a look at the install instructions. there are different requirements for different phones. It doesn't list the 8178 specifically, but then again, most sites that deal with headsets and Aastra phones don't either.

You've tried everything else. might as well give this a shot!
 
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