IBM MT/ST
| Company type | Product |
|---|---|
| Industry | Word processing, Office equipment |
| Predecessor | IBM Selectric typewriter |
| Founded | 1964 |
| Products | Magnetic Tape/Selectric Typewriter (MT/ST) |
| Parent | IBM |
The IBM MT/ST (Magnetic Tape/Selectric Typewriter, identified as MT72 in Europe) is a variant of the IBM Selectric typewriter that incorporates magnetic tape recording and playback mechanisms within an attached unit containing controls and relays. IBM introduced this model in 1964.
Description
Text is recorded on 1/2" magnetic tape cassettes with a storage capacity of approximately 25 kilobytes each, enabling users to perform editing and re-recording during playback. It holds the distinction of being the first device marketed as a word processor. Most versions come equipped with two tape drives, which support editing tasks and functions such as mail merge. An optional add-on provides a third tape station that records combined output from the two existing drives.
While the MT/ST offers automated word wrap, it does not feature a display screen, automatic hyphenation (although soft hyphen characters could be used), or an inherent page structure; users had to handle page breaks and numbering manually. Operators depended on auditory cues from the machine during playback. The backspace key allowed for character overwriting, including layered characters like á. Insertions were limited: text could be copied between tape drives or inserted using one reserved null character per line on a single tape. A "switch code" facilitated toggling playback between drives. Although it was possible to mark and navigate to specific tape positions, this process was somewhat unwieldy.
The MT/ST is fundamentally electromechanical, utilizing an array of electromechanical relays instead of purely electronic components.
In 1967, IBM engaged Jim Henson, creator of the Muppets, to produce a short film titled Paperwork Explosion that highlighted the MT/ST, accompanied by music from electronic music innovator Raymond Scott.
Due to its substantial acquisition cost, most clients opted to rent the MT/ST. It became outdated during the 1970s following the emergence of floppy disk-based systems, leading IBM to cease support in 1983.
Users
IBM's largest client in Germany, Allianz, utilized the MT/ST for generating form letters derived from pre-composed text. One notable example was "14 23 56," referred to as the "Death Tape," which contained condolence letters requesting documentation from survivors while assuring swift processing of insurance claims.
Len Deighton's 1970 Second World War novel Bomber holds the distinction of being the first novel created on a word processor, having been composed using the MT/ST.
Additionally, the MT/ST functioned as a data entry tool for early editions of the RILM Abstracts at the CUNY Graduate Center. The cartridges produced by the MT/ST were processed through an IBM 2495 Tape Cartridge Reader into an IBM System/360 mainframe, where they underwent further processing prior to printing.
MT/SC
The IBM MT/SC (Magnetic Tape Selectric Composer), launched in 1967, serves as an output device designed to play tapes recorded and edited on the MT/ST. Though similar in appearance to the MT/ST and equipped with a single tape reader, it replaces the Selectric typewriter with an IBM Selectric Composer, which was previously operated manually. This device employs specialized typeballs—distinct from those used in the Selectric—that offer three type sizes (10, 12, and 15 characters per inch), fractional spacing between words, bold, and italic styles (excluding bold italic), across a variety of serif and sans-serif fonts such as Bodoni, Univers, and Times Roman. It generates fully justified, camera-ready text; however, using the manual Composer required typing each line twice—first to measure spacing and then to apply it.
The MT/SC automates this process by printing at speeds comparable to the Selectric while justifying text through automated interword spacing adjustments. When paired with the MT/ST, it enabled swift production of camera-ready copy at costs accessible to small and medium-sized publishers. Nevertheless, altering typefaces or toggling italics necessitated halting the Composer twice per change—sometimes multiple times within a single sentence—resulting in slower operation. Typeface changes were manual actions based on operator expertise rather than encoded instructions, resembling conventional typesetting practices.
Its operation is governed by an electronic microprogrammed controller.
IBM 2495 Tape Cartridge Reader
The IBM 2495 Tape Cartridge Reader facilitates the transfer of MT/ST tapes into a System/360 environment. Equipped with a hopper and stacker capable of holding up to twelve cartridges, it automatically loads tapes within five seconds and operates at a speed of 900 characters per second for both reading and rewinding. This device interfaces with System/360 Models 30, 40, or 50 through a multiplexor channel. Data extraction from the 2495 was managed using the OS/360 utility IEBTCRIN.