GSM modem not issue handshake signal

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eeh - 08 Feb 2007 14:57 GMT

Hi,

I have a project which uses land line modems to collect status data
from a remote device to local PC program. It works quite fine until
recently our customers want to use GSM modem at remote device side. We
find that the local PC program fails to connect to the remote device.

I debug the connection and find that the remote device does not issue
handshake tone when the local PC program dials to the remote device.
The remote device does answer the call but does not issue the
handshake tone.

Could anyone give me some hints to help me solve this problem?

Thanks!

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John Henderson - 08 Feb 2007 19:47 GMT

> I have a project which uses land line modems to collect status
> data from a remote device to local PC program. It works quite
[quoted text clipped - 8 lines]
>
> Could anyone give me some hints to help me solve this problem?

Are you dialling the GSM modem's data number? As far as
incoming calls are concerned, the default number is for voice
calls only. To receive data calls, you must get get a data
number for the device, and dial that number instead.

John

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eeh - 16 Mar 2007 05:25 GMT

> > I have a project which uses land line modems to collect status
> > data from a remote device to local PC program. It works quite
[quoted text clipped - 15 lines]
>
> John

I have added a AT command at+csns=0 and then it works.

However, when I inserted another sim card which is from another
service provider, it is not working. The handshake tone cannot be
heard.

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John Henderson - 16 Mar 2007 05:50 GMT

> I have added a AT command at+csns=0 and then it works.
>
> However, when I inserted another sim card which is from
> another service provider, it is not working. The handshake
> tone cannot be heard.

Have you set up the incoming bearer service for use with the
single numbering scheme? Refer to the "AT+CBST" and its
parameter values, but I'd suggest "AT+CBST=7" is the place to
start.

Does this other service provider even implement the single
numbering scheme?

John

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eeh - 16 Mar 2007 08:57 GMT

> Have you set up the incoming bearer service for use with the
> single numbering scheme? Refer to the "AT+CBST" and its
[quoted text clipped - 5 lines]
>
> John

Yes, I have already set it

AT+CBST? return 7,0,1

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John Henderson - 16 Mar 2007 09:38 GMT

> Yes, I have already set it
>
> AT+CBST? return 7,0,1

I'm not sure you're going to get far with your

at+csns=0

command, even on the SIM where you get handshaking. A value of
zero for the "AT+CSNS" command indicates a voice call according
to GSM 07.07. A value of "4" specifies a data call.

It just might be possible to somehow pass data over a GSM voice
call at _very_ slow speed (I have never tried). Does the
handshaking progress to a "CONNECT"? If so, what's the
reported throughput speed for the connection?

Normally you'd require a data call, which has the necessary
"data-friendly" characteristics. And usually that's achieved
by calling a data number. But the "single numbering scheme"
seems to offer the possibility of establishing both voice and
data calls to a combination voice/data number. I was not aware
that any provider offered this service.

John

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eeh - 16 Mar 2007 09:51 GMT

> > Yes, I have already set it
>
[quoted text clipped - 21 lines]
>
> John

Sorry!

at+csns=4 is right!

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John Henderson - 16 Mar 2007 10:10 GMT

> at+csns=4 is right!

A data call. Excellent! Just what you need.

The simplest explanation for its not working with another
provider is that they don't support the "single numbering
scheme". You could ask them what their procedure is for
routing data calls to their customers. They may have to
subscribe to a dedicated data number. This is the method that
I'm familiar with.

John

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eeh - 16 Mar 2007 10:53 GMT

> > at+csns=4 is right!
>
[quoted text clipped - 8 lines]
>
> John

Thank you very much!
I think your suggestion is correct.
I will try it.
Bye!

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eeh - 23 Mar 2007 14:39 GMT

> > at+csns=4 is right!
>
[quoted text clipped - 8 lines]
>
> John

I have obtained a new SIM card. The card is surely having data service
as my friend claimed that it is being used in some repeater devices.

I have tried to connect the wireless modem from my PC modem and found
that the connection has no ring tone and connection handshaking tone.
Is it possible that a connection does not require them?

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