I am trying 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 does, I am missing the
boat on how to do it properly.
So, I have a question: Is it possible to either (a) do the double
modulation as listed above, or (b) provide recorded wav or gsm sounds as
a background fill while a phone is being rung? I have recordings of
various types of older central office ringback tones that I'd just love
to be able to put into Asterisk.
I know this sounds a bit arcane. But Asterisk can do so many things to
order that it really ought to be able to do this, don't you think?
Thanks,
Greg
