IBM 557

IBM 557

The IBM 557 Alphabetic Interpreter [http://www.tietokonemuseo.saunalahti.fi/eng/kuva_16_eng.htm (photo)] allowed holes in punch cards to be interpreted and the Hollerith punch 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 punch 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 bin.
*Selective Line PrintThe 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 punch tab card was 80 columns, but there were exceptions.

Maintenance

The 557 was a maintenance headache. In reality it was 60 little printers. The sequence was as follows:

#The punch card was fed from the card hopper and read by means of an electrical voltage placed onto a metalContact Roll’, timing controlled by aMaster Circuit Breaker, and 80Read Brushes’, one brush for each card column, andWire Contact Relayswhich decoded the data.
#The punched card acted as an insulator and the electrical circuit was only completed in the presents of a punched hole. A Control Panel (plug-board) controlled what function was to be performed by directing the impulse to a series ofwire contact relayswith the impulses de-coded according to the Hollerith code. (Mark Sense could not provide the current needed topicka wire contact relay and so needed vacuum tubes to amplify the current). After the card was read, aCard Gatemoved 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, amechanical baildriven by large steel cams would raise 60 gearedlifter barswhich engaged 60rackswhich engaged 60intermediate gears’, which drove 60print wheels’. (You can see the maintenance problem with 60 of just about everything). The lifter bars were then lowered under spring tension by themechanical bailin time with the reading of the punched card. Using the impulse from thecontact roll’ / ‘card brush’ / ‘wire contact relaycircuitry, apush rodwould latch (stop) the individuallifter baron its downward motion with the character to be printed correctly positioned on the print wheel and facing 1 of 60print hammers’. Analignment bailwould then seat itself in between the teeth of theprint wheelsto perform vertical alignment.
#Acard shieldwould grab the punch card to hold it in place and lower it a position almost touching the inked print ribbon and print wheel. At the correct time 60hammers’, under spring tension and controlled by a cam, wouldfirepressing 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 theprint shieldinto thetransport beltsand moved to thestacker bin’.

The 557 was prone to jamming of the lifter bars and resulted in what the CEs called aRack & Wheeljob. 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

ee also

* Unit record equipment
* IBM 550 Numeric Interpreter


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