[Asterisk-Users] Don't forget the TDM400P power connection

[Rich Adamson]

> The way it was explained to me is that the voltages required to generate the
> ringer singals is quite high, so an external power feed is required.

Technically, old style ringers require about 90 volts AC, with multiple
ringing frequencies ranging from 20 hz to about 66hz (mostly related to
the old party-line ringing methods). Central Office ringing generators
typically kicked out more like 100-to-110 volts of AC.

More then what anyone would care to know... ;)