[time-nuts] He is a Time-Nut Troublemaker....

[Hal Murray]

> Cool.  I used systems like this (but a bit faster) for measuring
> detonation velocity in explosives.  Several wires would run through an
> explosive compound and would break as the material detonated.  Later
> the systems used the same wires but would measure the voltage/current
> running through them as the explosive detonated in a magnetic field. 

Speaking of timings and explosions...

Early Ethernets used coax with transceivers at the coax and a drop cable down 
to the computer.  One of the problems was that a short in the transceiver or 
the attachment could kill the whole segment.  They were a pain to debug.

Some early host adapter cards had a TDR feature.  It didn't cost much.  It 
was basically just a counter that started when you started transmitting a 
packet and stopped when the transceiver said "collision".  It wasn't great, 
but could at least get you close.

I've heard stories that the TDR feature was used to collect timing data on 
some A-bomb tests.  The bomb was at the bottom of a hole.  An ethernet cable 
went down the hole.  I can't remember or reconstruct the details.  I assume 
there was a PDP-11 at the top of the hole.  The idea is something like you 
send a packet to trigger the bomb, and when the bomb goes off, the cable 
vaporizes and is no longer terminated so packets turn into collisions and the 
TDR grabs the time.

It sounds like an urban legend, but it's a fun one.




-- 
These are my opinions, not necessarily my employer's.  I hate spam.