MC55_ATC_V04.00 Page 406 of 475 3/17/06
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17.7 AT+VTS DTMF and tone generation
AT+VTS is intended to send ASCII characters or strings which cause the Mobile Switching Center (MSC) to trans-
mit DTMF tones to a remote subscriber. The command can only be used during active voice calls and offers the
following variants: 
• AT+VTS=<dtmfString> allows to send a sequence of DTMF tones with a duration defined with AT+VTD. 
• AT+VTS=<dtmf>[,<duration>] allows to send a single DTMF tone. In this case, the duration can be ind-
vidually determined during the call. 
Syntax
Parameter Description
String of ASCII characters in the set 0-9,#,*,A, B, C, D. Maximal length of the string is 29. The string must be
enclosed in quotation marks ("...").
ASCII character in the set 0...9,#,*, A, B, C, D.
Tone duration in 1/10 seconds with tolerance. If not specified current setting of AT+VTD is used. 
The minimum duration of DTMF signals is 300ms. DTMF tones below 300ms cannot be generated. 
1...255
Test Command
AT+VTS=?
Response(s)
+VTS: (list of supported<dtmf>s), (list of supported<duration>s)
OK
Write Command
AT+VTS=<dtmfString>
Response(s)
OK
Write Command
AT+VTS=<dtmf>[, <duration>]
Response(s)
OK
ERROR
+CME ERROR
Reference(s) PIN ASC0 ASC1 MUX1 MUX2 MUX3 Charge  Last
GSM 07.07 ! % % % % % ! ! !
<dtmfString>
(str)
<dtmf>
(str)
<duration>
(num)