The IBM 557 Alphabetic Interpreter allowed holes in punch cards to be interpreted and the Hollerith punch card characters printed on any row or column, programmed by the means of a wiring plug board. 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. Download high resolution version (950x367, 41 KB) This is a copyrighted and/or trademarked logo. ...

The IBM 557 was an immensely complex electro-mechanical unit record machine. It contained large arrays of vacuum tubes (valves), wire-contact relays, cams, interlocks and gears. It hosted complex mechanisms called the rack and wheel unit, and the print unit. Engineers maintaining these machines were specially trained to repair them. In Australia, the last two engineers ever to be trained on these these were IBM engineers David Byrne and Winston Chin-Lenn in late 1979. Before the advent of electronic computers, data processing was performed using electromechanical devices called unit record equipment, electric accounting machines (EAM) or A data processing shop would have at least one of most of the machine types. ... In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal. ... Automotive style miniature relay A relay is an electrical switch that opens and closes automatically under control of another electrical circuit. ... Epirus (Greek Ήπειρος, Albanian ria), a province in northwestern Greece (a Greek periphery) bounded by West Macedonia and Thessaly to the east, by the Ambracian Gulf and the province of West Greece to the south, the Ionian Sea and the Ionian Islands to the west and Albania to the north. ... A gear is a toothed wheel designed to transmit torque to another gear or toothed component. ...

There are no 557's operating commercially in the world today.

In the way of elaboration on the IBM 557:

As a Customer Engineer with IBM in NYC in the 60s & 70s I worked on many a 557 problem. For those interested, the standard model of the 557 was an all electro-mechanical piece of IBM ‘unit record’ equipment and only used vacuum tubes when a feature call Mark Sense was installed. Mark Sense was a feature where the 557 could read lead penciled marks placed by hand in small, slanted, pre-printed ovals on the 80 column punch card and then print the de-coded information on the card. I saw very few 557s with the Mark Sense feature.

Other features available: 1) Proof - Where the 557 verified, again through electrical mechanical means, that the information printed was correct. 2) Multiple Stacker - The printed card could be placed in a selected output bin. 3) Selective Line Print – The standard 557 could only print on the top 2 horizontal lines. Selective Line print feature allowed you to print on one of 26 lines. 4) 40 or 60 column card read. Standard punch tab card was 80 columns, but there were exceptions.

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

1) The punch card was fed from the card copper and read by means of an electrical voltage placed onto a metal ‘Contact Roll’, timing controlled by a ‘Master Circuit Breaker, and 80 ‘Read Brushes’, one brush for each card column, and ‘Wire Contact Relays’ which decoded the data.

2) The punched card acted as an insulator and the circuit was only completed in the presents of a punched hole. The impulse was sent through a series of ‘wire contact relays’ and the impulses de-coded according to the Hollerith code. (Mark Sense could not provide the current needed to ‘pick’ a wire contact relay and so needed vacuum tubes to amplify the current). After the card was read, a ‘Card Gate’ moved into the card path to stop the card for printing on the correct horizontal line.

2) As the card was being read and positioned for printing, a ‘mechanical bail’ driven by large steel cams would raise 60 geared ‘lifter bars’ which engaged 60 ‘racks’ which engaged 60 ‘intermediate gears’, which drove 60 ‘print wheels’. (You can see the maintenance problem with 60 of just about everything). The lifter bars were then lowered under spring tension by the ‘mechanical bail’ in time with the reading of the punched card. Using the impulse from the ‘contact roll’ / ‘card brush’ / ‘wire contact relay’ circuitry, a ‘push rod’ would latch (stop) the individual ‘lifter bar’ on its downward motion with the character to be printed correctly positioned on the print wheel and facing 1 of 60 ‘print hammers’. An ‘alignment bail’ would then seat itself in between the teeth of the ‘print wheels’ to perform vertical alignment.

3) A ‘card shield’ would 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 60 ‘hammers’, under spring tension and controlled by a cam, would ‘fire’ pressing the card / inked ribbon onto the print wheel and leaving a 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.

4) The printed card is then released by the ‘print shield’ into the ‘transport belts’ and moved to the ‘stacker bin’.

The 557 was prone to jamming of the lifter bars and resulted in what the CEs called a “Rack & Wheel” job. This meant stripping the machine down to its base and rebuilding it, an 8 hour job. You also said a little prayer that when you re-assemble the 557 and tested it, that the machine would not jam again, (which would happen once in awhile).