If I understand the question, I think he is liiking to generate SIT tones (Special Information Tone) use by many telco's ahead of announcements for wrong numbers, disconnected numbers, all circuits busy and on-and-on.
Do a google search and you will find out the frequency, duration and cadence of the most common types. US and foreign specs aer slightly different frequencies, but the difference is minimal well within the detectable scope of the autodialers used.
If you are looking to defeat telemarketer auto dialers, you can simply download the tones, and transfer them to an answering machine ahead of your announcement and it works quite well. If you are in the USA, the Do-Not-Call registration list works even better, but I used the above trick for 2 years prior to the list being available.
Dialtone