Synopsis:

       SMplaydigits(vox_chan,digit_str,[inter_dur_ms,dig_dur_ms])

Arguments:

       vox_chan – The voice channel

       digit_str – The string of DTMF digits to play

       [inter_dur_ms] – The gap between digits (in millseconds)

       [digit_dur_ms] – The digit duration in milliseconds

Description:   This function plays the string of DTMF digits specified in the digit_str argument.      The optional inter_dur_ms and dig_dur_ms  allow for the delay between digits and the digit duration to be specified (in milliseconds).   If these are omitted or set to 0 then the Aculab default durations are used.

Returns:  Returns 0 upon success or negative error code.