http://www.gcn.com/archives/gcn/1999/May10/41.htm
Little bit down the page...
"The first videoconferencing system, from Compression Labs Inc. of San Jose, Calif., arrived in 1988 to link the New Mexico and California facilities."
Compression Labs doesn't seem to have a web site of their own, but I found address and phone number on business.com
Compression Labs, Inc.
2860 JUNCTION AVENUE
SAN JOSE, CA
+1 408 4353000
+1 408 9225429
They also deal with high-end military applications and include work on satellite, microwave, and cable systems. If you can reach anyone there, I'm sure they've got some info worth looking into.