Synopsis:

       SMctlPulse(vox_chan,on_off)

Arguments: 

       vox_chan:  The voice channel

       on_off -  Set to 0 to turn pulse detection off (default) or 1 to turn pulse detection on

Description:  This function allows pulse detection to be switched on or off.

Returns:  Returns 0 on success or -1 if a bad vox_chan was specified.