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From: hsw@SPARTA.COM (Howard Weiss)
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  can anyone identify this mystery box?
Message-ID: <9101141541.AA00361@katahdin.columbia.sparta.com>
Date: 14 Jan 91 15:41:07 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 20

The ECU was an Error Control Unit that allowed hosts to be separated from
their respective IMPs (now packet switch nodes) on the ARPANET/MILNET.
Using the distant host interface, the host to packet switch interface
could only drive a signal about 2000 feet (which was a great improvement
over the 30 feet that was achievable with local host interfaces).  The
ECU allowed a host to be separated by a larger distance and still look
like it was a locally attached host.  Basically, the ECU converted the
ARPANET 1822 interface signalling into an SDLC which was then recoverted
into 1822 by the distant end ECU.  ECU's were always used as pairs - one
on the host end and one on the IMP end.

ACC at the time was Associated Computer Consultants and they are now
known as Advanced Computer Communications.  Sorry, don't have a phone
number.

Howard Weiss

SPARTA, Inc.
Columbia, MD 21046
hsw@sparta.com