N.B. Joss@netcom.com was not acceptable to netcom At 1:13 PM 6/13/96 -0800, Norman Hardy wrote:

EMP (Electro Magnetic Impulse), a side effect of nuclear devices, is purportedly able to damage electronics over distances of many miles. Some weapons may be designed to enhance this.

I vaguely remember hearing that a nuclear device exploded high over the midwest would have significant EMP effects over half the continental USA. When a USSR pilot flew a "state of the art" fighter out and US intelligence got their hands on it we were surprised that all the electronics were vacuum tubes. However, vacuum tubes are highly resistant to EMP. (They arc between elements, rather than fry like ICs.)

Faraday cages attenuate EMP by the same factor that they attenuate secrets. I think that if a blast doesn't damage the cage then neither will the EMP. Of course the cage may survive but fail to protect the interior (insufficient attenuation). I don't know whether a cage sufficient for tempest is sufficient for EMP protection. Comm lines and power cables go thru the cage and cause problems here as well. Perhaps hefty surge protectors suffice here. Communications equipment outside the cage should at least be equipped to recover quickly upon transient error and not tear donw circuits. Normal error control can then hopefully compensate for the transient. (IP, ATM, Frame relay??)

Makes you want fiber optic comm cable. Protection inside the cage probably depends on how powerful the EMP is. However, the need for some degree of stealth in Class III InfoWar will limit the strength of the EMP. ------------------------------------------------------------------------- Bill Frantz | The Internet may fairly be | Periwinkle -- Consulting (408)356-8506 | regarded as a never-ending | 16345 Englewood Ave. frantz@netcom.com | worldwide conversation. | Los Gatos, CA 95032, USA