Synopsis:

       SMgettones(vox_chan[,max_tones])

Arguments:

       vox_chan – The voice channel

       [max_tones] – optional argument specifying the maximum number of tones to return from the foreground buffer

Description:   This function works in conjunction with the SMwaittones() function to receive DTMF input.        The SMgettones() function will return all of the digits that have been copied to the foreground buffer by a call to SMwaittones(),  or the number of tone specified by max_tones if this argument is specified.

Returns:  Returns the string of DTMF digits from the foreground buffer or -1 if an invalid vox_chan was specified.