TV Typewriter | 1973

SWTPC CT-1024

 The TV Typewriter is a video terminal that can display two pages of 16 lines and 32 uppercase characters on a standard television. This design gained significant attention when it was featured on the cover of Radio-Electronics magazine in September 1973. The magazine included a six-page description of the design, and readers could receive a 16-page production detail package by mail for $2. Radio-Electronics sold thousands of copies of this package, and the TV Typewriter is considered an important milestone in the home computer revolution alongside the Mark-8 and Altair 8800 computers.

Sometimes, the term is used generically to refer to interactive computer displays shown on screens. Before the development of CRT displays, teleprinters were the standard output medium.

The designer of the TV Typewriter was Don Lancaster, an engineer at Goodyear Aerospace. He conceived the TV Typewriter while designing military high-resolution video displays. At that time, affordable microprocessors and solid-state memory were not widely available, so the system used small-scale integrated circuits with TTL digital logic and shift register memory. Most of the circuits were used to synchronize the timing of an analog generator that outputs data bit by bit from memory. The text displayed on the screen was generated by the Signetics 2513, one of the first character generation ICs.

The article was published in the September 1973 issue, and in addition to the six-page article, readers could pay $2 to receive the complete 16-page layout plan. Initially, it was expected that only about 20 copies of this plan would be sold, but due to overwhelming reader requests, a total of 10,000 copies were sent out. Compared to professional terminals costing over $1,000 at the time, the $120 kit seemed quite affordable.

In the November issue, the magazine apologized for delays in shipping the booklet and provided information on parts suppliers for readers who had difficulty sourcing components. It also answered readers' questions and provided additional features and usage ideas for the TV Typewriter. The December issue included corrections to the TV Typewriter booklet, which were included in subsequent publications.

The TV Typewriter was a challenging project for hobbyists due to its compact design and complex circuitry. However, many people completed the project, and some connected it to Intel 8008-based computers. The April 1975 issue of Micro-8 Newsletter included methods for connecting the TV Typewriter to Mark-8 or SCELBI computers, along with user modifications. The original TV Typewriter design did not include serial interfaces, modem connections, or offline data storage capabilities, but Don Lancaster addressed these in the September 1975 issue of BYTE magazine and his TV Typewriter Cookbook. The serial interface board was featured in the February 1975 issue of Radio-Electronics.

In 1973, standardized keyboards were not readily available at affordable prices. New keyboards were primarily used by computer and terminal manufacturers, and hobbyists often used Baudot or EBCDIC codes instead of ASCII. The TV Typewriter project did not include a keyboard, and the keyboard project featured on the cover of the September issue was introduced by Don Lancaster in the February 1973 issue, which involved handcrafting 55 key switches. Most hobbyists modified surplus keyboards to generate ASCII codes. Don Lancaster's original prototype TV Typewriter is currently on display at the Computer History Museum, and the keyboard there is equipped with an ASCII encoder circuit, which was featured in the February 1974 issue of Radio-Electronics.

In the April 1974 issue of Popular Electronics, a complete keyboard kit designed by Don Lancaster was introduced, which was sold by Southwest Technical Products for $39.50. The first version used simple RTL ICs to decode the key matrix, but this design was later improved to use more advanced keyboard encoder ICs.

SWTPC CT-1024

SWTPC initially started by selling a circuit board set for $27 and eight major integrated circuits for $49.50, requiring hobbyists to source the remaining components themselves.

The original TV Typewriter was difficult to assemble, and as some ICs became obsolete, Southwest Technical Products decided to redesign the kit. This new design was introduced in Radio Electronics under the name "TV Typewriter II" over six issues starting in February 1975. This time, readers did not need to order separate schematics, as the entire design was serialized in the magazine.

Daniel Meyer of SWTPC recruited Ed Colle, an engineer who had worked on terminal design at Datapoint, to lead the new TV Typewriter design. The SWTPC CT-1024 terminal could display 32 characters x 16 lines and provided a fixed screen without scrolling. This terminal used common TTL components and 2102 static RAM, with a loose component layout and wide traces to facilitate assembly. A variety of option board sets were also offered, including a serial interface. The keyboard was based on Don Lancaster's design, while the rest of the terminal design was handled by Ed Colle.

The design was completed by the end of 1974, and kits began to be sold in December 1974. The first advertisement for the CT-1024 appeared in the January 1975 issue of Popular Electronics, facing a page featuring the Altair 8800 computer. The complete kit, including options, was sold for just $275, gaining significant popularity, and the improved CT-64 model was released in 1977. The CT-64 offered scrolling capabilities and the ability to display 64 uppercase and lowercase characters in a single line.

By 1975, Don Lancaster had contributed over 100 articles to magazines such as Popular Electronics and Radio-Electronics. He also wrote a book on digital design called RTL Cookbook in 1968. Register-Transistor Logic (RTL) was an early integrated circuit (IC) technology that was later replaced by TTL, and in 1974, he published TTL Cookbook. This book was published for 20 years and sold over a million copies.

The original TV Typewriter was designed before affordable RAM became available, so it quickly became outdated. Don Lancaster made many design improvements, which he published in 1976 in a book titled TV Typewriter Cookbook. Some of the content from this book was serialized in the first issue of Byte magazine. The TV Typewriter Cookbook served as a guide for designing video computer terminal systems and was divided into chapters such as:

"Some Basics"

"Integrated Circuits for TVT Use"

"Memory"

"System Timing – Calculation and Circuits"

"Cursor and Update Circuits"

"Keyboards and Encoders"

"Serial Interfaces"

"Television Interfaces"

"Hard Copy and Color Graphics"

This book helped many hobby developers and professionals design video displays for home computer systems. The cassette interface design in Chapter 7 became the basis for the Kansas City standard. The circuits in this book were based solely on TTL without using microprocessors. In 1978, TV Cheap Video Cookbook introduced the TVT 6 5/8 design compatible with 6502 or 6800 microprocessors, targeting the KIM-1 microcomputer.

The cover of the original TV Typewriter book featured an ASCII keyboard designed by Don Lancaster, which was sold by Southwest Technical Products. The early computer store chain Byte Shop added its logo to the cover of the book and sold the TTL Cookbook and TV Typewriter Cookbook in their stores. Subsequent versions of the cover were designed for Radio Shack stores. The ninth printing of the first edition occurred in 1983.