search for: 420hz

...rying to get Asterisk to emulate the sounds of the earlier telephone systems, and the settings in [us-old] are pretty helpful. The only thing lacking is ringback tone, which is not quite as complex as the real phone systems of the day. For example, it is true that a ringback tone commonly used is 420Hz modulated by 40Hz. This is what shows up in [us-old]. But that modulated tone was generally overlaid on top of real ringing, i.e. 20Hz. So, using the Asterisk example of 420*40, it would seem that a decent ringback would be (420*40)*20. But, of course, that doesn't appear to exist. If it d...