DTMF and Programmable Tone Generation

The following functions support tone generation on the VPB:

Tones (including DTMF) tones are generated on a channel using the vpb_settone() function. All of the standard DTMF tones are defined at initialization. Other user defined tones can be programmed at any time using the vpb_settone() function. The standard DTMF tones can also be reprogrammed using the vpb_settone() function. The tone generator parameters are constant across all VPB channels, they are not programmable on a channel by channel, or board by board basis. Up to 10 programmable tones can be defined, giving a total of 26 tones including the standard DTMF tones. Each tone can consist of up to 3 frequency components, each with independent amplitude, specified in dB with respect to the overload level of 0dB. There are limits in the tone generator parameters. Attempting to program a tone outside of these limits will generate an error.