Tube modular vs. safety

[Paul Perry]

I remember a ditzy secretary/receptionist when I was
working in an earlier life as an investment analyst
(in the 60s) who would idly suck on the end of the 
phono plugs in the antique switchboard, get a 50v 
boot thru her fillings, burst into tears, and get the 
rest of the day off.

Personally, for a valve analog system, looking at
pictures of the old machines, they didn't take too many 
precautions that I could see. But, the big systems had 
'patch panels' where you set the problem up on a
jackfield about a foot or two squrare, then clamped this 
to the system. So you could have someone loading another 
problem while yours was working. And, you could load it
without having to touch any active leads.

The real problem for valve analog gear was noise and
dynamic range, so that is why they had the 100v standard.
Later the transistor took over and it went to +-10v.

paul perry Melbourne Australia 

BTW there are a few analog computers in museum collections
now, search analog+computer+museum in eg google.