LTE Module SeriesEC25&EC21 AT Commands ManualEC25&EC21_AT_Commands_Manual 191 / 231ParameterExampleATD12345678900; //DialOKAT+VTS="1" //The remote caller can hear the DTMF toneOKAT+VTS="1234567890A" //Send multiple tones at a timeOK12.5. AT+VTD Set Tone DurationThe command sets the duration of DTMF tones. It can also set time interval of two tones when sendingmultiple tones at a time.Reference3GPP TS 27.007<dtmfstring> ASCII characters in the set 0...9, #, *, A, B, C, D. The string should beenclosed in quotation marks ("...").When sending multiple tones at a time, the time interval of two tones can be specified by AT+VTD. The maximal length of the string is31.<duration> The duration of each tone in 1/10 seconds with tolerance.The value ranges from 0 to 255.If the duration is less than the minimum time specified by the network, theactual duration will be the network specified time.If this parameter is omitted, is specified by AT+VTD.AT+VTD Set Tone DurationTest CommandAT+VTD=?Response+VTD: (0-255),(0-255)OKRead CommandAT+VTD?Response+VTD: ,OK
