Thank you for visiting The History of Computer Communications. We are in the process of updating this site with additional content, improved navigation, and easier access from mobile devices.
The new site will go live July 1st, 2021.

Enter your email address to learn about future updates and the publication of Circuits, Packets & Protocols: Entrepreneurs and Computer Communications, an updated and edited version of this history to be published in late 2021 by the Association for Computing Machinery.

Custom Search


Table of Contents
Market Sectors
Supporting Documents
Computer History Museum

CHM Home Page
Oral History Archive



Each Product category in each market sector can consist of hundreds of competing alternatives; alternatives in the functionality of the product, in the underlying technology used to create the product, in the features of the product and in the number of manufacturers selling the product. For example, in the high speed lease-line modem category many speeds are available, such as 9600 bits per second (bps), which can be implemented in one of several technologies, each of which can offer dozens of different features and is offered by sale by dozens of manufacturers. The same is true for all the categories of products in Computer Communications. The choice of which products to focus on in this historical reconstruction is aided by hindsight with the most successful products and technologies selected.


The history of Data Communications...

is told primarily through the story of three product categories: lease-line modems, statistical multiplexers and T-1 multiplexers. Curiously, even though all statistical multiplexers required the use of modems, invariably lease-line modems, and users of lease-line modems invariably used statistical multiplexers, few firms truly innovated both lease-line modems and statistical multiplexers. Codex was the exception. Likewise, few firms innovating statistical multiplexers made the leap to innovating networking T-1 multiplexers, the class of T-1 multiplexers to dominate. Micom became a very successful firm making the leap to a low-cost statistical multiplexer and yet first had to try reselling a T-1 multiplexer from another company before buying a firm innovating a different T-1 multiplexer. Why existing firms fail to innovate next generation products or products in categories co-evolving with their own is of particular interest in this history. No Data Communication firm successfully innovated either Networking or Internetworking products; successful as in products that achieved meaningful marketshares.

Lease-Line Modems
Beginnings of Modem Competition: Codex and Milgo 1956-1967 1.1
Codex and Milgo: Needing Money 1967-1968 1.5
Codex and Milgo Become Public Companies 1968 1.8
Codex Encounters Unexpected Problems: 1969 3.4
Codex Turns the Corner: 1970 3.6
Firms and Collective Behavior: The Creation of the IDCMA 1971 3.9 
Codex and the 9600: 1971 3.10
ADS Falls on Hard Times: 1971-1972 3.11
Codex Passes a Milestone: 1972 3.12
Data Communications 1972 3.13
Codex: LSI modems and Front-End Processors 1973 5.3
Codex: The LSI Modem and Competition 1974-1975 5.5
Codex: The Statistical Multiplexer and Competition 1975-1976 5.8
Modems, Multiplexers and Networks 1976-1978 5.9
Codex and Motorola 1977-1978 5.11
Multiplexers - Time Division and Statistical
Multiplexer Innovation: American Data Systems 1966-1968 1.6
ADS Has a Blockbuster 1969 3.5
ADS Hits a Wall: 1970 3.7
Data Communications 1972 3.13
Wesley Chu and the Statistical Multiplexer 1966-1975 5.4
ADS: Rebirth as Micom 1973-1976 5.6
Modems, Multiplexers and Networks 1976-1978 5.9
Micom: The Statistical Multiplexer 1976-1978 5.10
Micom: Meteoric Success and Competition 1978-1979 5.12
Data PBX's
 Micom: The DataPBX and IPO 1978-1981 7.14
Codex: The DataPBX 1978-1981 7.15
The Data Communication Competitors 1981-1982 8.12
 Micom 8.13
Codex 8.14
The Data Communication Competitors: 1983 – 1984 10.13
Codex 10.14
Micom 10.15
T-1 Multiplexers
Data Communications 1979-1988 11
Bridges 12.4
Gateways and Routers 12.5

The history of Networking...

is the central history of this book and is closely observed as a technology trajectory from packet switching through Ethernet, then standards making and finally the resolution of networking protocols. How successfully the firms of Data Communication competed in Networking as well as how well the firms of Networking fared in Internetworking will also be a focus. The firms that dominated Networking were the ones that innovated local area networks (LANs), specifically Ethernet, although in the beginning hundreds of alternative products were offered to interconnect computers. The Data Communication firms sold DataPBXs, a product derived from their multiplexer technologies. It garnered early market leadership before being eclipsed by LANs. Ethernet LANs had to fend off many competing local area networking technologies, including the presumed winner, token ring, to be sold by IBM. The start-ups and the computer company, Digital Equipment Corporation (DEC), won the battle, in large measure by being first to the market with a product offering the best combination of functionality and price.

Robert Metcalfe and the Founding of 3Com 7.11
Robert Pliner and the Founding of Sytek 7.12
Ralph Ungermann and Charlie Bass and the Founding of Ungermann-Bass 7.13
Sytek: a Broadband Network and Needing Cash 7.16
Ungermann-Bass: Xerox, Broadband and Needing a Chip 7.17
3Com: Product Strategy and Waiting for a PC 7.18
Emerging LAN Competition - 1981 8.1
3Com, Ungermann-Bass and Sytek - 1981 8.8
The Early LAN Competitors - 1982 8.16
A Second Wave of LAN Competitors - 1982 8.20
3Com, Ungermann-Bass and Sytek - 1982 8.30
Ethernet Chips, Boundless Hope and Market Confusion 8.34
3Com, Ungermann-Bass and Sytek - 1983-1984 10.2
The Early LAN Competitors 1983-1984 10.6
The Second Wave of Competitors 1983-1984 10.10
State of Competition - 1985 10.17
3Com, Ungermann-Bass and Sytek - 1985-1986 10.18
The Early LAN Competitors 1985-1986 10.22
The Second Wave of Competitors 1985-1986 10.26


The history of Internetworking...

while just beginning as the historyof this reconstruction is concluded, in 1988, is again one of hundreds of firms entering the market and a few start-ups coming to dominate: notably cisco and Wellfleet. The very nature of what internetworking meant was a disputed question in the early years as many pundits and manufacturers believed the market was one of interconnecting voice communication products. And while voice-focused T-1 multiplexers jumped out of the starting blocks first, it would be the "true" products of Internetworking - bridges and routers - that would come to dominate and even quickly incorporate T-1 multiplexing as one of their features. Again the firms of Data Communications would get it wrong, just as they had in Networking. Why?

T-1 Multiplexers
Data Communications 1979-1988 11
Bridges and Routers
Internetworking 1983-1988  LANs over WANs 12