When would I need an external resource to generate DDI and/or CLI digits while using CAS?

If you wish to implement DTMF or MFC register signalling, you will need some sort of external resource to generate/detect the DTMF or MFC tones. The resource needs to be connected to the voice channel sometime during each call setup to detect or play the tone-based digits.

To aid developers, Aculab introduced an optional DSP daughter module solution for Aculab digital network access PCI cards. The daughter module is automatically used during the call setup process to play or detect tones that are conveyed along the voice channels. Tone based digits are sent automatically by simply calling the call_openout function and supplying a valid destination and/or origination address into the out_xparms structure. Incoming digits can be obtained by calling the call_details function.

On download, if the firmware is configured for DTMF or MFC register signalling (default), it will check for the existence of an Aculab DSP daughter module. If one does not exist, the firmware download will fail.

Note: If you do not have an Aculab DSP daughter module fitted, then the only way CAS firmware can be downloaded is if it is configured for decadic dialing (See CAS firmware release notes regarding the -s98 switch).