[Asterisk-Users] feature - VM gain adjust?

[Lyle Giese]

Let's see you have 11.2 db of loss from the phone you are using to call in
on and the FXO interface on Asterisk.  Retreiving voice mail would add
another 11.2 or a total of 22.4 db.  But your measured tone level was 36db.

In other words the FXO interface and Asterisk introduced about 14 db of
loss.  I would find this amount of loss to be unacceptable.  Rather than
hack at the code, why not find this additional loss?  A PBX or telco switch
should not introduce this much loss, IMHO.

Lyle

----- Original Message ----- 
From: "Rich Adamson" <radamson at routers.com>
To: "Asterisk-a-users-list" <asterisk-users at lists.digium.com>
Sent: Sunday, July 11, 2004 6:00 PM
Subject: [Asterisk-Users] feature - VM gain adjust?


>
> I'm toying with adding a feature request to provide some sort of
> gain setting for voicemail when accessed from "certain" interfaces.
> Maybe something like voicemail=6.0 (db) within a specific channel
> section of zapata.conf corresponding to a pstn line.
>
> Situation:
> 1. Someone calls into asterisk and leaves a voicemail. The sound
> is recorded at some volume well below 0 db, and is directly related
> to the distance asterisk is from the central office (pstn cable
> loss) plus whatever distance the user placing the call is from
> his/her central office.
> 2. I receive a text message that a voicemail was left.
> 3. I call into asterisk remotely (assume from a cell phone) and
> retreive the voicemail. My location creates another xx db of loss
> between myself and asterisk, and voicemail can hardly be heard.
>
> Actual Measured Values:
> 1. Asterisk is 5.6 db from the central office. Called from one
> pstn line, through the central office, to asterisk and sending a
> 1004 hz tone at 0db. Recorded the tone into voicemail. (Tone should
> have been recorded at about 11.2db, two times the cable loss)
> 2. Called into asterisk again, this time to retreive the voicemail
> and measured the 1004 hz tone from voicemail. It was -36db "actual".
> This retreival added another 11.2db of loss due to pstn interfaces
> and plant loss.
> 3. The calls were through a TDM FXO module with rx and tx gains
> set to 0. (Changing rx and tx gain to +3 db and repeating the test
> resulted in a measured -30.5db signal, but these settings create
> unwanted echo issues. Therefore adjusting channel gain is not an
> option.)
>
> The end result is that retreiving any voicemail message left from
> a distant location and retreived from a distant location can hardly
> be heard. By adding the proposed voicemail=6.0 statement to the
> appropriate channel, any calls connected to voicemail via that
> channel would effectively increase transmission levels by 6db (or
> whatever the setting happened to be). In this example case, the
> setting would increase the vm volume by 12db (or about 24db measured
> in the above).
>
> Anyone have any thoughts on this?
>
> Rich
>
>
>
>
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