DTMF decoding on GSM MODEM..

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DTMF decoding on GSM MODEM..

Postby bappa on Tue Sep 20, 2005 3:23 pm

how to decode DTMF tones received via GSM modem?will decoding circuit for landline telepohone work on GSM MODEM?i m using FARGO MAESTRO 20 (voice call support)
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GSM modems

Postby Tomi Engdahl on Thu Sep 22, 2005 12:31 pm

So called "GSM modems" are pretty different things than those normal telephone line modems. Actually those "GSM modems" are not modems at all in the classical sense, they do not do any modulation/demodulation for the signal.

The GSM modems are more like data format converters / interface converters. They convert the serial communications data between serial port (or USB, IR, Bluetooth etc..) and the data format used in GSM network. A GSM modem with serial interface does around this when transmitting data: receives several characters of data coming from serial ports (amount from zero charaters to maximum that can be put to one GSM data packet, how manu received within set timeframe), put them to GMS data packet (includes adding header information, error correcting code, maybe encrypting/scrambling etc..). Then push it the ready packet to the digital GSM radio circuitry to send it out at right time (within the time slot given by base station system for this phone to use).
On the other end the electronics receiovs the packets, decodes them (removes headers, does error correcting, etc..) and puts received characters to serial port transmitting buffer to be sent out though serial port at needed data rate.

This is how communiction with two GSM modems that have serial ports would do. This kind of processing to both diretions.

When the "GMS modem" need to communicate with a normal telephone modem, the communication works as described above to a serial port on the operator premisses that is connected to an ordinary telephone line modem (in real life systems the "GMS modem" electronics, telephone line modem and controle electronics are all integrated to one single circuit board insalled to equipment rack, possibly one circuit board holdign electronics for many lines).

Traditional DTMF decoding tricks do not work with GSM modems.
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Re: DTMF decoding on GSM MODEM..

Postby HM Maruff on Sun Dec 18, 2005 8:56 am

You can find some DTMF Decoder information from this URL
http://www.gsm-modem.de/dtmf_decoder_gsm.html
and in
http://www.gsm-modem.de/dtmf-gsm.html
HM Maruff
 

Re: DTMF decoding on GSM MODEM..

Postby ANUSUYA on Wed Jan 04, 2006 11:59 am

bappa wrote:how to decode DTMF tones received via GSM modem?will decoding circuit for landline telepohone work on GSM MODEM?i m using FARGO MAESTRO 20 (voice call support)

I WANT ALSO HOW IS WORKING EPABX SYSTEM WITH DETAILS
ANUSUYA
 

Postby Xtel on Fri Feb 03, 2006 9:53 pm

I am looking for DTMF decode on CDMA and can't find any information.
Does andyone here know what to do?
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Re: DTMF decoding on GSM MODEM..

Postby [email protected] on Thu Oct 08, 2009 5:18 pm

how do i use my dstv decoder as a modem for internet connectivity
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Re: DTMF decoding on GSM MODEM..

Postby Sugar70 on Fri Dec 10, 2010 1:10 am

same situation here, any help would be very appreciated here.
Thanks,,,


how to deal with depression
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