IBM 557
The IBM 557 Alphabetic Interpreter (photo) allowed holes in punched cards to be interpreted and the punched card characters printed on any row or column, selected by a control panel. The machine was a synchronous system where brushes would glide over a hole in a punched card and contact a brass roller thereby setting up part of a character code. There are no 557's operating commercially in the world today.
Available features
- Proof - Where the 557 verified, again through electrical mechanical means, that the information printed was correct.
- Multiple Stacker - The printed card could be placed in a selected output stacker.
- Selective Line Print â The standard 557 could only print on the top 2 horizontal lines (between the 12 and 11 rows and between the 11 and 0 rows). Selective Line print feature allowed you to print on one of 26 lines.
- 40 or 60 column card read. Standard punched card was 80 columns, but there were exceptions.
- Master/detail printing. Text on a master card could be printed on following detail cards.
Maintenance
The 557 was a maintenance headache. In reality it was 60 little printers. The sequence was as follows:
- The punched card was fed from the card hopper and read by means of an electrical voltage placed onto a metal âContact Rollâ, timing controlled by a âMaster Circuit Breaker, and 80 âRead Brushesâ, one brush for each card column, and âWire Contact Relaysâ which decoded the data.
- The punched card acted as an insulator and an electrical contact was only completed in the presence of a punched hole. A control panel controlled what function was to be performed by directing the impulse to a series of âwire contact relaysâ with the impulses de-coded according to the Hollerith code. (Mark Sense could not provide the current needed to âpickâ a wire contact relay and so needed vacuum tubes to amplify the current). After the card was read, a âCard Gateâ moved into the card path to stop the card for printing on the correct horizontal line.
- As the card was being read and positioned for printing, a âmechanical bailâ driven by large steel cams would raise 60 geared âlifter barsâ which engaged 60 âracksâ which engaged 60 âintermediate gearsâ, which drove 60 âprint wheelsâ. (You can see the maintenance problem with 60 of just about everything). The lifter bars were then lowered under spring tension by the âmechanical bailâ in time with the reading of the punched card. Using the impulse from the âcontact rollâ / âcard brushâ / âwire contact relayâ circuitry, a âpush rodâ would latch (stop) the individual âlifter barâ on its downward motion with the character to be printed correctly positioned on the print wheel and facing 1 of 60 âprint hammersâ. An âalignment bailâ would then seat itself in between the teeth of the âprint wheelsâ to perform vertical alignment.
- A âcard shieldâ would grab the punched card to hold it in place and lower it a position almost touching the inked print ribbon and print wheel. At the correct time 60 âhammersâ, under spring tension and controlled by a cam, would âfireâ pressing the card / inked ribbon onto the print wheel and leaving an inked impression of the character on the surface of the punched card. There is a blank space on the print wheel for non-printing columns.
- The printed card is then released by the âprint shieldâ into the âtransport beltsâ and moved to the stacker.
The 557 was prone to jamming of the lifter bars and resulted in what the CEs called a âRack & Wheelâ job. This meant stripping the machine down to its base and rebuilding it, an 8 hour job.
References
- http://www.columbia.edu/acis/history/interpreter.html
- IBM 557 Alphabetic Interpreter Reference Manual A24-0516-1
See also
- Unit record equipment
- IBM 550 Numeric Interpreter