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SDK: Fax CED and CNG tones

When Fax machines (or Fax modems or Fax servers) first connect they exchange tones called the CED (called station identification) and CNG (calling tone). These tones are really there to confirm that the other party really is a fax machine and not (for example) a human operator.

A calling fax machine plays the CNG tone, a short 1100Hz tone that is periodically repeated. An answering fax machine plays the CED tone, a high-pitched (2100Hz) long tone. Examples of these tones are attached to this article.

In the Diva SDK, CED is known as DivaAnswerTone and CNG is known as DivaFaxCallingTone. Both tones can be interpreted and generated by a Diva Media Board (although DSPs are needed for this function).  These are continuous/extended tones that are reported when extended tones are enabled (e.g. DivaReportTones).

If you have DTMF reporting on (e.g. DivaReportDTMF), these tones are also reported as pseudo-DTMF digits: CED tone is reported as 'Y' and CNG tone as 'X'.