🚀 go-pugleaf

In article <PHR.92Oct28031754@napa.telebit.com>, phr@telebit.com (Paul Rubin) writes:
|> A co-worker of mine brought up an interesting idea.
|> He thinks it might be very difficult to intercept data
|> by tapping a phone line of someone using a modern high
|> speed full duplex modem.  The reason is that the full
|> available bandwidth of the phone line is being used
|> in both directions; the modems separate out the signals
|> with echo cancellation, which means that the modem
|> takes the phone signal and subtracts what it itself
|> is sending--the difference is what the other modem
|> is sending.  But a wiretapper might have an awfully
|> hard time of separating the two signals.  
|> 
|> Any thoughts?

I can think of one approach right off:  Take two taps separated by
a few feet, and subtract them delayed by the wire's propagation delay.
This is known as a "directional coupler."  You can read both directions
if you have two.
-- 
Eric Weaver  Sony AVTC  677 River Oaks Pkwy, MS 35  SJ CA 95134  408 944-4904
& Chief Engineer, KFJC 89.7 Foothill College, Los Altos Hills CA 94022
-- 
Eric Weaver  Sony AVTC  677 River Oaks Pkwy, MS 35  SJ CA 95134  408 944-4904
& Chief Engineer, KFJC 89.7 Foothill College, Los Altos Hills CA 94022