At 11:43 1/4/96 -0600, Jason Rentz wrote:

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With a tightly focused beam (light is easy, I don't know about lower frequencies), you can prevent interception except by very obvious physical devices. (e.g. Someone in a cherry picker truck.) You may be able to avoid the need to encrypt the link (and all the paranoia about key management, advances in factoring etc. that that implies.)

Bill

The problem with this comes when you start creating links between much taller buildings like in San Fran. Any give building over 30 stories might sway a foot or so at any given time. Combine that with the other building and you might get a few feet of movement. (movement not including during an earthquake) :)

(1) No single communication technology is appropriate for every problem. (2) A technical fix could include having the receiver send steering orders to the transmitter. This solution would, of course, be a long way from the low tech scavenged lens and 1/2 meter cardboard mailing tube technology I was thinking of. Bill