During the 1965-66 school year at University High School in Minneapolis, teachers installed a Model 33 ASR teletype.
The machine looked like a sturdy typewriter and produced a steady clatter as it typed onto paper.
Using its keyboard and a long-distance telephone connection, students logged in to Dartmouth College’s time‑sharing mainframe computing network in New Hampshire.
In early 1967, 18 school districts around Minneapolis and St. Paul formed a cooperative called the Minnesota School Districts Data Processing Joint Board, known as Total Information for Educational Systems (TIES).
They shared the costs and computer resources of the Sperry-Rand UNIVAC (Universal Automatic Computer) 1110 located in the St. Paul area.
A West Central Tribune article May 12, 1967, described TIES’ purpose as “establishing and conducting a data processing center for the service of said school districts and other school districts located in the state of Minnesota.”
Using standard telephone lines and acoustic modems to link teletype terminals with distant mainframes, multiple school districts established dial-up connections that allowed them to share computing power for both administrative tasks and classroom teaching.
The teletype served as both an input device and output printer, allowing students to type commands and receive responses from the remote mainframe computer on paper.
By having school districts share the costs of the Sperry-Rand UNIVAC mainframe hardware, software, and technical support, interactive computing was made available to schools that otherwise could not afford it.
By late 1967, TIES was serving more than 130,000 students.
Central to that classroom experience was the Model 33 ASR (Automatic Send-Receive) teletype terminal, made by Teletype Corporation, an AT&T subsidiary.
These electromechanical machines transmitted seven-bit ASCII (American Standard Code for Information Interchange) over telephone lines at 110 baud to remote mainframe computers.
To put it in perspective, sending data at 110 baud, about 10 characters per second or 0.00011 Mbps, was over 900,000 times slower than a typical 100 Mbps home internet connection today.
While the Model 33 ASR sent and received data as electrical signals over the telephone line to and from the remote mainframe, the teletype contained no microprocessor or modern digital logic.
Instead, it used electromechanical circuitry.
Incoming serial data was received as start-stop pulses, typically at 110 baud, and passed through a distributor mechanism that synchronized the signal with the machine’s internal motor-driven timing.
Each seven-bit ASCII character, along with start and stop bits, was decoded by a series of selector magnets that actuated mechanical linkages, cams, and code bars.
These components positioned the print mechanism to strike the correct character on paper.
The same signals could also drive the paper tape punch, where hole patterns encoded each character for storage and later playback.
A Model 33 ASR terminal cost around $1,000 at the time, equivalent to about $10,750 today.
To connect to the remote mainframe, the terminal used either a built-in call-control unit, which included a rotary telephone dial, mode selector, and line controls, or an acoustic coupler with a standard telephone handset on the line.
With the built-in call-control unit, the user placed the call directly from the teletype itself. With an acoustic coupler, the user dialed on a standard telephone, waited for the answering tones, then set the handset into the teletype’s rubber cups so the modem could send and receive data over the line.
Because telephone networks carried analog signals while computers communicated digitally, a modem converted the teletype terminal’s outgoing digital data into analog audio tones for transmission over the phone line, then demodulated incoming tones from the remote mainframe back into digital data.
The teletype didn’t have a screen; instead, it printed both the student’s input and the computer’s output on long rolls of light-yellow canary paper.
The Model 33 ASR featured a built-in eight-hole punched-tape reader and punch, which functioned as an early form of offline data storage.
As students typed, it punched one‑inch‑wide paper tape with hole patterns encoding each character, allowing them to save and later reload their programs into the mainframe without retyping them during a dial‑up session.
The 1970-71 school year saw more than 26,000 students logging into the TIES computer network.
TIES formed one of the nation’s first school-based online communities, learning and sharing BASIC (Beginners’ All-purpose Symbolic Instruction Code) and FORTRAN (Formula Translation) programs, information, and messages across school districts.
The computer network let students across Minnesota exchange messages and programs, including math games, YAHTZE (a computer version of Yahtzee), and simulations such as “Hamurabi,” “Sumer,” “Lunar Lander,” and “Star Trek.”
In 1971, Minnesota student teachers Don Rawitsch, Bill Heinemann, and Paul Dillenberger created “The Oregon Trail. “
Heinemann and Dillenberger programmed it in HP (Hewlett-Packard) Time-Shared BASIC on a Minneapolis school district minicomputer, while Rawitsch handled research and design.
In 1973, the Minnesota Legislature created the Minnesota Educational Computing Consortium (MECC) to expand computer access for students across the state.
That same year, MECC spent about $7 million (roughly $50 million today) on a UNIVAC 1110 mainframe built by Sperry Rand’s Univac division in St. Paul, installing it at 1925 Sather Street in Lauderdale, Minnesota.
This powerful mainframe computer became the heart of MECC’s groundbreaking statewide time‑sharing mainframe computing network, giving hundreds of schools remote access to educational software.
To manage long-distance toll costs, MECC used AT&T Wide Area Telephone Service, or WATS, and Foreign Exchange, or FX, lines through the telephone company.
WATS provided national inbound 800-number access to the mainframes through the early toll-free service AT&T established in May 1967.
FX lines were dedicated circuits used for in-state connections, letting a school connect its teletype to the dial tone of a remote telephone exchange where the mainframe’s number was local.
That allowed the school to call the mainframe as if it were in the same exchange, avoiding regular long-distance toll charges.
Like WATS, FX service was billed at a flat monthly rate, which was lower than standard long-distance toll-call charges.
A personal note: while working at the Winsted Telephone Company, we installed and maintained many national inbound and outbound WATS lines and state FX lines for local businesses, most of them tied to the Twin Cities’ large toll-free metro calling area.
During the 1970s, Winsted only had toll-free calling to Lester Prairie.
The Blooming Prairie Times reported April 23, 1975, that math and biology students used a teletype machine connected by modem to Austin High School, which relayed data to the UNIVAC 1110.
By 1977, the UNIVAC 1110 at 1925 Sather Street was retired due to high user demand and system latency that prevented it from meeting MECC’s performance contract.
It was replaced by the Control Data Corporation Cyber 73, which supported up to 448 simultaneous connections, more than 5,000 daily sessions, and approximately 2,000 teletype terminals across the statewide network.
In 1978, schools began shifting from remotely accessed mainframes to compact stand-alone microcomputers, allowing districts to own their machines and eliminate dial-up costs and latency.
MECC sought bids for a standard classroom computer and received proposals from Radio Shack, Commodore, and Apple.
International Business Machines (IBM) did not bid, as its personal computer would not be released until 1981.
MECC selected the Apple II and purchased 500 units for $649,000 ($3.4 million today).
The TIES cooperative, which first gave Minnesota students access to a central time‑sharing mainframe computing network, dissolved in 2018.
Today, the clatter of teletypes lingers only in memory, yet the digital pathways forged by those early telephone lines and circuitry laid the foundation for Minnesota’s first school‑connected computer network.
