| http://www.w3.org/ns/prov#value | - In the United States, Canada, and other countries in the North American Numbering Plan (NANP), the standard PSTN ringback tone is generated by summing a 440-Hz tone with a 480-Hz tone and applying these to the telephone line in a two-second on and four-second off cadence.The tone combination produces a warbling ring ... ring ... ring sound, caused by the 40-Hz beat, or interference due to the di
|
