Synopsis:

       SMctlCPtone(vox_chan,on_off)

Argument:

       vox_chan –  The voice channel

       on_off – set to 0 to turn call progress tone detection off (default), 1 to turn it on

Description:  This function turns on (1) or off (0) call progress tone detection that corresponds to a member of the set of call-progress tones currently recognisable by the module.   Note that call-progress tone detection may not be used simultaneously with tone or digit detection on the same channel.   

See Prosody API documentation for sm_listen_for() for the set of preloaded call progress tones.

Returns:  0 if successful or -1 if invalid voice channel speicified.