Telenet
| Company type | Public |
|---|---|
| Industry | Telecommunications, Computer networking |
| Founded | August 16, 1975 |
| Founder | Bolt Beranek and Newman (BBN) |
| Fate | Acquired by GTE in 1979; later acquired by Sprint and rebranded as Sprintnet |
| Headquarters | Reston, Virginia , United States |
Area served | United States, United Kingdom (London node) |
Key people | Bob Kahn (initial president), Larry Roberts (president), Barry Wessler |
| Products | Public packet-switched network, Telemail email system, PC Pursuit service |
Telenet was an American commercial packet-switched network that commenced operations on August 16, 1975. Recognized as the first public data network licensed by the FCC in the United States, it catered to both governmental and commercial organizations by linking their computer systems via dedicated lines to its core network. Additionally, public dial-up access was accessible in numerous cities across the U.S.
History
After the U.S. authorized commercial "value added carriers," Telenet Inc. was established by Bolt Beranek and Newman (BBN), the same firm responsible for ARPANET's packet switching infrastructure. In January 1975, following a two-year development phase, Telenet Communications Corporation obtained venture capital funding. The company’s initial president was Bob Kahn, who was later succeeded by Larry Roberts. Barry Wessler, also from ARPA, joined the leadership team. The company launched the nation’s first public data network in August 1975.
Telenet provided an email system known as Telemail and originally operated out of Washington, D.C., before moving its headquarters to McLean, Virginia. In 1979, it was acquired by GTE and subsequently relocated to Reston, Virginia. Following acquisition by Sprint and rebranding as "Sprintnet," Telenet's customer base transitioned onto Sprint’s advanced IP network, Sprintlink, which played a significant role in shaping the modern Internet infrastructure.
Coverage
At its inception, the network operated switching nodes in seven major U.S. locations: Washington, D.C. (which housed the network operations center), Boston, New York City, Chicago, Dallas, San Francisco, and Los Angeles. These nodes were supported by Telenet Access Controller (TAC) terminal concentrators positioned both onsite and remotely. By 1980, Telenet had expanded to over 1,000 switches, exceeding Southern Bell’s network of approximately 250 switches.
In 1977, Telenet extended its reach internationally by establishing a node in London along with a Network Control Centre integrated within Britain's Post Office Telecommunications.
Internal network technology
Initially, Telenet utilized a proprietary virtual connection host interface featuring statically defined hop-by-hop routing and employed Prime commercial minicomputers as switching devices. The system later evolved to incorporate a custom-designed multiprocessing switch based on 6502 microprocessors. This switch included a patented arbitrated bus interface that formed a switched fabric among processors—an innovative architecture that offered a technological edge well before standards like PCI Express emerged.
Most interswitch connections operated at speeds of 56 kbit/s, while critical links such as New York to Washington ran at T1 rates of 1.544 Mbit/s. Early versions of the switching tables required rebooting switches to update network topology; subsequent software improvements allowed for updating tables without interrupting service. However, dynamic routing protocols were never implemented; instead, fault tolerance was maintained through multiple static routes per switch. Network management functions continued to rely on Prime minicomputers.
The company’s founders and executives actively participated in international efforts to standardize packet-switched data communication protocols. Soon after the X.25 protocol was published in March 1976, Telenet adopted it—becoming the industry’s first to offer an X.25 host interface—thereby solidifying its position in public data networking markets. Internally, Telenet operated a proprietary variant of X.75 and maintained standard X.75 gateways to other networks, enabling interoperability across its global services.
Fundamental asynchronous connectivity
Users connected to Telenet through modems utilizing the Public Switched Telephone Network, dialing into TAC ports from either terminals or computers emulating terminals. Enterprises with numerous local terminals often deployed an on-premises TAC, linked via dedicated circuits at speeds reaching 56 kbit/s to the closest Telenet switch. Initially, dial-up modem rates were capped at 1200 bit/s, later advancing to 4800 bit/s.
For example, a user in New York City could place a local call and then access a system by inputting a command such as:
| c 301 555 |
which would connect them to system number "555" within the 301 area code.
Among prominent clients were early internet service providers like The Source, which capitalized on Telenet’s reduced nighttime tariffs to offer cost-effective services, as well as Quantum Link (the predecessor of AOL).
Additional access protocols
Telenet accommodated remote concentrators for IBM 3270 terminals communicating over X.25 with proprietary applications running on IBM 370x front-end processors. It also provided support for Block Mode Terminal Interfaces (BMTI) tailored for IBM Remote Job Entry terminals operating with 2780/3780 and HASP Bisync protocols.
PC Pursuit
During the late 1980s, Telenet launched PC Pursuit, a subscription service with a fixed monthly fee that enabled users to dial into Telenet’s network in one city and then connect through modems located in another city. This allowed access to bulletin board systems and various services without incurring long-distance call charges, effectively broadening market accessibility by simulating local calls across different metropolitan areas.
Subscribers entered a five-letter city identifier composed of a two-letter state abbreviation followed by a three-letter city acronym, for instance, OHCLV for Cleveland, Ohio. Once connected, they could dial any local telephone number as if they were directly connected within that city.
| City Code | Area Code(s) | City |
|---|---|---|
| AZPHO | 602 | Phoenix, Arizona |
| CAGLE | 818 | Glendale, California |
| CALAN | 213 | Los Angeles, California |
| CODEN | 303 | Denver, Colorado |
| CTHAR | 203 | Hartford, Connecticut |
| FLMIA | 305 | Miami, Florida |
| GAATL | 404 | Atlanta, Georgia |
| ILCHI | 312, 815 | Chicago, Illinois |
| MABOS | 617 | Boston, Massachusetts |
| MIDET | 313 | Detroit, Michigan |
| MNMIN | 612 | Minneapolis, Minnesota |
| NCRTP | 919 | Research Triangle Park, North Carolina |
| NJNEW | 201 | Newark, New Jersey |
| NYNYO | 212, 718 | New York City |
| OHCLV | 216 | Cleveland, Ohio |
| ORPOR | 503 | Portland, Oregon |
| PAPIT | 412 | Pittsburgh, Pennsylvania |
| PAPHI | 215 | Philadelphia, Pennsylvania |
| TXDAL | 214, 817 | Dallas, Texas |
| TXHOU | 713 | Houston, Texas |
| WIMIL | 414 | Milwaukee, Wisconsin |
| WASEA | 206 | Seattle, Washington |