4 Requirement

23.0143GPPRelease 17Support of Dual Tone Multi-Frequency (DTMF) signallingTS

Dual Tone Multi Frequency (DTMF) is an inband one out of four plus one out of four signalling system, primarily used from terminal instruments in telecommunication networks. The international recommendations which apply are ETSI ES 201 235 [3, 4, 5] as detailed in subclauses 6.2 and 6.3. For PCS 1900 for North America the Standards which apply are operator specific.

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.

The use of DTMF is only permitted:

– when the speech teleservice is being used or during the speech phase of alternate speech/data and alternate speech/facsimile teleservices; the DTMF is transmitted across the radio interface as specified in subclause 6 of this specification; and

– during a multimedia call; the DTMF is transmitted across the radio interface using the H.245 UserInputIndication message (see ITU-T H.245 [6]). This is transparent for the MSC.

The responsibility for checking this lies in the MS.