Modem Based Crypto Telephones

[Phil Karn]

It's true, dialup modems are becoming so fast that low bit rate vocoders
may well prove unnecessary for a secure phone with good voice quality. But
vocoders are still handy for allowing the use of a slower modem (e.g., over
impaired lines, such as those with a lot of taps :-)) and for freeing up
bandwidth that you might want to use for other purposes (e.g., data).

Phil