A Method to Send DTMF Tone While a 3G Call?

In the 3GPP system the MSC must support DTMF in the mobile to land direction.

The support of this facility in the land to mobile direction is for further study.

If you are in North America the PCS 1900 networks applications of the standard are operator specific.

You must be in a call that has a component of speech.

This information is available on 3GPP in TS 23.014 version 9 from 2009.

The standards can be viewed by searching for them.

Your sentences are incomplete and unclear. If you were a little more specific someone might be able to help you. When asking about wireless phones it makes a difference if you are talking about a Mobile Station (MS) going to the Base Station (BS) or the other way around. The digital phones have the option of sending the signaling across the air interface and not necessarily through the audio (speech) system. I think that means that the DTMF tone is not actually sent around the world but rather that the instructions for a specific pair of tones is sent, then the audio is constructed at the other end.

If you are doing some sort of control device then you would want to research if the entire path can send the signaling you need in every circumstance and for every operator. That is a lot of work. If you are doing work in a vehicle then you would want to contact a major vendor of installed vehicle modem systems, they usually have a department that takes care of just this sort of problem. Of course, you have to buy an awful lot of parts from them to get their attention.

You could build a hardware DTMF generator from a kit (see http://www.boondog.com/tutorials/dtmf/dtmf.htm) and tape the speaker over the microphone of the telephone. That will work for any telephone, mobile or land-based, though it would be slightly less convenient. You could then lay out the buttons to suit your preferred control configuration.

jsolar's responses on the subject are very good.

The issue is not really clear. Where do you want to send the DTMF tones? To the number you are calling or to another number? In fact, your mobile phone will send DTMF tones -- that's how you access other functions, such as three way calling. But that probably won't help you. In that case, the tones are going to the switch to set up the call, not to whatever you are trying to control.

And what do you mean by 3G call? A voice call or data call? Most providers will not allow a voice call during a data session. In North America, it is possible to get 3G data while on a voice call (GSM Networks with HSPA only), but not vice versa. Not possible on CDMA. There, it is generally either voice or data, not both. The exception comes in when you have a smart phone/PDA that can operate on two networks simultaneously -- such as your voice service and Wi-Fi or 4G.