[ih] Arpanet physical connectors

[Vint Cerf]

at Stanford my PDP-11/20 was connected by VDH to an IMP in another building
on the campus.

v


On Thu, Jul 23, 2020 at 9:56 AM Steve Crocker via Internet-history <
internet-history at elists.isoc.org> wrote:

> Much of this has been covered already in responses to your note, but we can
> add a little more.  The connectors were definitely NOT RS-232.  The BBN
> team designed the connector.  I believe they wanted it to be as simple as
> possible.  It was bit serial, operating at 100 kilobits per second.  The
> lines connecting the IMPs operated at 50 kilobits per second, so 100 kb/s
> was a reasonable fit.  Making it run much faster wouldn't have made a
> noticeable difference in the overall performance.  The interface was
> designed to operate up to 50 feet from the host.  A different interface was
> designed later to operate up to, I think, 1000 feet.  These were referred
> to as the Local Host (LH) and Distant Host (DH)  interface.  A third
> version was designed yet later to operate over unlimited distance.  It was
> called the Very Distant Host (CDH) interface.
>
> I believe Severo Ornstein and Ben Barker were the key hardware people at
> BBN.  Mike Wingfield at UCLA built the first host interface for our Sigma
> 7.  All are copied on this message.  BBN Report 1822 has the details, as
> reported in other messages.
>
> As noted, each site had to figure out how to connect the IMP into its
> host.  This required a separate design and implementation at each of the
> initial sites, and thus it was indeed important to have competent EE people
> involved.  After a while, ACC and DEC and perhaps others started to make
> interfaces available for various hosts.
>
> Steve
>
>
> On Thu, Jul 23, 2020 at 8:02 AM Stephane Bortzmeyer via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> > https://twitter.com/nielstenoever/status/1286254151874293760
> >
> > Dear Internet History nerds, what did the connectors and cables of the
> > ARPAnet look like?
> >
> > Were these serial cables? Seems likely because the RS-232 standard dates
> > back to 1960.
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> >
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