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Recording from GSM phone?

Last response: in Technologies
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August 8, 2004 11:02:25 PM

Archived from groups: alt.cellular.gsm (More info?)

Hello,

I need to record both sides of some of my cellular phone
conversations, using my Siemens S46 GSM phone. I also have a 2.5mm
headset adapter for this phone.

I tried using a Diasonic digital recorder with its included cell
headset/adapter, but the recordings were full of hum and buzz. I also
purchased
a specialized black-box recording adapter from Radio Shack, but this
had the same problem.

I later was told that this happens with all GSM phones when you try to
use the audio output directly for recording, that there is something
inherent in the hardware or software that produces an interfering hum
and buzz.

Does anyone know about this, and why there is this problem? And does
anyone know how to get a decent recording from the GSM phone?

Thank you.

More about : recording gsm phone

Anonymous
August 9, 2004 6:51:47 AM

Archived from groups: alt.cellular.gsm (More info?)

Robert wrote:
> I tried using a Diasonic digital recorder with its included cell
> headset/adapter, but the recordings were full of hum and buzz. I also
> purchased
> a specialized black-box recording adapter from Radio Shack, but this
> had the same problem.
>
> I later was told that this happens with all GSM phones when you try to
> use the audio output directly for recording, that there is something
> inherent in the hardware or software that produces an interfering hum
> and buzz.

This is an inherent problem for GSM's transmission method. The radio wave
interferes with audio feeds. You can try to filter it, or use a cordless
headset adapter.
Anonymous
August 9, 2004 10:32:46 PM

Archived from groups: alt.cellular.gsm (More info?)

On 8 Aug 2004 19:02:25 -0700, r@starcenter.com (Robert) wrote:

>Hello,
>
>I need to record both sides of some of my cellular phone
>conversations, using my Siemens S46 GSM phone. I also have a 2.5mm
>headset adapter for this phone.
>
>I tried using a Diasonic digital recorder with its included cell
>headset/adapter, but the recordings were full of hum and buzz. I also
>purchased
>a specialized black-box recording adapter from Radio Shack, but this
>had the same problem.
>
>I later was told that this happens with all GSM phones when you try to
>use the audio output directly for recording, that there is something
>inherent in the hardware or software that produces an interfering hum
>and buzz.
>
>Does anyone know about this, and why there is this problem? And does
>anyone know how to get a decent recording from the GSM phone?
>
>Thank you.

YOu need to very very carefullly shield the audio line coming off the
handset, and the recording device itself. GSM is a time division
multiple access technology, when on, it it transmits at the rate of
217 tiimes per second, and if you don't protect the audio lines, you
get envelope detection, and a 217 Hz buzz from the transmitter in the
phone. Outside the USA, where they don't have part 15 to contend
with, you can often hear a radio in the room, or on the nightstand go
off with a 217hz buzz just before your phone rings, or when the phone
is 'paged'...
!