IBM 557
| Company type | Product |
|---|---|
| Industry | Data processing equipment |
| Founded | 1954 |
| Products | Punched card reading and printing machine |
The IBM 557 Alphabetic Interpreter, launched in 1954, was designed to read holes in punched cards and print the corresponding characters on any chosen row or column through a control panel. This synchronized mechanism utilized brushes sliding over punched holes to make contact with brass rollers, which then generated character codes.
Features
- Proof – electrically and mechanically confirmed printed data
- Multiple Stacker – routed printed cards into designated output bins
- Selective Line Print – enabled printing beyond the top two lines, up to 26 lines
- 40 or 60 column card read – supported non-standard punched card formats
- Master/detail printing – permitted printing text from a master card onto following detail cards
Maintenance
The 557 was a complex device requiring intensive upkeep, essentially consisting of 60 miniature printers. The operation involved:
- Cards were fed from the hopper while data was read via electrical contacts on a metal ‘Contact Roll’ and 80 ‘Read Brushes’, with decoding performed by ‘Wire Contact Relays’.
- Acting as insulators, the cards only completed circuits where holes existed. A plugboard directed signals to relays that interpreted Hollerith code. For Mark Sense cards, vacuum tubes amplified the current. A ‘Card Gate’ paused the card for accurate line printing.
- Steel cams drove a mechanical bail that lifted 60 geared ‘lifter bars’, which engaged racks and gears to rotate 60 ‘print wheels.’ Each lifter bar latched at the correct character position aligned with one of 60 ‘print hammers.’ Vertical print alignment was maintained by an ‘alignment bail.’
- A ‘card shield’ pressed the card against an inked ribbon and print wheel; at the precise moment, 60 spring-loaded hammers struck to imprint characters onto the card. Columns without printing corresponded to blank spaces on the print wheels.
- After printing, the card was released onto transport belts and conveyed to its assigned stacker.
Frequent jams in the lifter bars necessitated extensive "rack and wheel" repairs—disassembling and reassembling could take up to eight hours—creating considerable operational difficulties.
See also
- Unit record equipment
- IBM 550 Numeric Interpreter