interface a mobile phone to fixed line

[meshmesh]

dear all, did anyone tried to interface a mobile phone to fixed line ( PSTN) and carry voice signal on the fixed line ..?

with regards
meshmesh

 

[cancel]

hi .. try to search fot gsm pstn gateways ... there are many of out there ... one big problem is that noise comming from tx us significant

 

[meshmesh]

I succeeded to make an AT connection to my mobile phone with a little circuit with no problem .. S35 phone for example has Speaker out and mic in pins but I don't know how to dial , carry voice on the pstn or detect ringing signal without damaging the phone ..

do you know one of these gateways ..?

With regards
meshmesh

 

[artem]

The comming noise is the confort noise sent from network to mobile when discontinued transmission is used or when no speech signal is going on between mobile and network. It could be important when duplexer is threshold activated ( let say hands free kind of implementation ) .But if hybrid transformer solution is applied and gain will be adjusted , it should not be big problem .

If you are trying dialin into to another volatile
in PSTN network , some tricks must be done about how to transfer destination number from mobile .
Of course caller Id will help you , but it is fixed .
DTMF tones can not be properly passed from network to mobile because speech optimized vocoder is used . May be prior to MS could be sent with destination number .
But no problems does exist with PSTN to mobile call where PSTN guarranties DTMF tones passing (if not DCME equipment - vocoder alike - is used between originating and destination entities ).

Have a close look to PSTN telephone's speech schcematics - it will give idea what to use in duplexer. The rerst is about handling AT commands from mobile .

 

[Igor_S]

You can start the dialing sequence, start/end the call, send SMS and much more via serial RS232 interface. Try to find the list of commands supporting by your specific mobile phone. You can than implement any PIC with serial interface in order to do this job.

 

[redfred]

Try Zarlink, they have ics especially for this application.

 

[cesare]

Almost all modern phone have a serial port with standard GSM AT commands.

So it should be simple to implement the software to drive the phone.

Take a look at www.silabs.com. Their proslic component is very well suited to develop WLL

 

[Rayengine]

On top of AT commands, many item is needed to clarify likes NOKIA
it has MBUS and FBUS! The new one is ACI.

 

[trend]

Has anyone completed this circuit and care to share their knowledge with me?

I am comfortable with the hardware side.. but lack the software side to actually make a voice connection.

Any help would be awesome!!

thanks-Lee

 

[stephen_h]

For software side, it is the major the AT command which is easy available from the internet. There has a special trick to deal with ACI-phone (NOKIA) because of the two-line bi-directional communications. I also look for this kind of information.