[ih] Arpanet physical connectors

Jack Haverty jack at 3kitty.org
Thu Jul 23 10:00:31 PDT 2020

On 7/23/20 8:53 AM, Noel Chiappa via Internet-history wrote:
> To start with DH (by far and away the most common), IMPs had a specified round
> 'female' plug (a mil-spec connecter, available from AMP - like the one in the
> URL Carsten provided - I think the axact part number is in the documemtation),
> mounted on the back of the IMP somewhere. 
I remember these connectors well, because of a strange experience I had
involving them.  

They were big, sturdy, heavy, expensive military-grade connectors.   I
don't remember the part number though.   Computer interconnecting cables
in that era were often large and unwieldy.  E.g., the PDP-10 bus cables
to interconnect processor, memories, storage cabinets et al were huge,
and quite expensive.

At one point in the 80s, I was in charge of a contract to build and
deliver some equipment using the same connectors, in order to be
compatible with the IMPs.   We had a tight schedule, with the contract
requiring delivery of the first units 12 months after signing the

Not expected to be a problem.    Except..... we quickly discovered that
those particular connectors were readily available through the usual
channels --- with a lead time of 60 weeks to delivery!   Apparently such
military-grade connectors are only built when needed, and unless we
ordered 10,000 or so they wouldn't schedule a special manufacturing
run.   We should have ordered them before we submitted the proposal I guess.

So much easier these days.  After all there's not all that many
different flavors of USB physical connectors!  All available with one or
two day delivery too.


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