Shuffling machine
The randomness or otherwise of cards produced from automatic shuffling machines is the subject of considerable interest to both gamblers and casinos.
A widely reported, but unpublished, study by Persi Diaconis and Susan Holmes in 2000 resulted in the redesign of many shuffling machines.
[citation needed] Patents regarding card shuffling devices started to appear in the United States around the end of the 19th century.
The device simulated a riffle shuffling by extracting the cards through a slot at the bottom of each box and placing them in a pile in the middle.
The operator would turn a crank which was connected to gears and finally disks covered with rubber that were in contact with cards.
This feeding mechanism ensured that the final stack was composed of cards "randomly" coming from the left or right chamber.
One year later, William Ranney proposed another version of his device where the original deck was split in half and cards would fall from one or both halves at once.
John Bowen proposed in 1899 a compact "card shuffling machine" where the unshuffled pack was enclosed between two horizontal plates.
Fred C Rollings in 1899 invented a device with a rotating table where cards were spread around the center using a detent with variable pressure.
[7] In 1901, Benjamin Bellows filed a patent for his device which used "gravity alone for all movements of the cards" by dividing guiding them through moving compartments.
[8] Various mechanisms were proposed during the following years with different combinations of rollers, card-holding boxes, combs and pins systems.
In 1925, Charles and William Gunzelmann filed a patent for a simple rhombus-shaped apparatus where the cards were inserted in an upper chamber.
His patent description provides interesting insights regarding the problems related to previous machines: If the cards were worn or bent, the shuffling could fail.
To increase randomness, the author proposes to use a set of different selector plates or to use another deck being shuffled while people are playing.
In 1934, Ralph Potter invented an electromechanical machine that would read perforated cards and generates random sequences.
During the rest of the 1930s, many inventions tried to address the dealing problem, mainly by using rotating frames that would distribute cards to each player around the table.
Both domains must fulfill mathematical requirements regarding randomness to avoid known patterns, repeated sequences and other kind of statistical weaknesses or biases.
Signals from electrical noise sources (like a hot cathode gas discharge tube or a resistor) would typically be sent through filters and amplifiers to output one or several random streams.
According to the patents filed during the 1950s and 1960s, designers created simple devices where a basic shuffling operation was repeated several times (by feeding the output deck back into the machine) instead of having one complex pass implying many tricky mechanical operations ending up with a poor shuffling and lower reliability.
In 1974, David Erickson and Richard Kronmal proposed a shuffler based upon a logic circuit with binary gates.
[15] The deck was placed in a holder and cards were extracted one by one, sent into a downward slope channel containing some flaps that would be activated or deactivated, depending upon which stack should be fed.
In 1985, Edward Sammsel proposed a machine that extracted the cards from the bottom of two deck holders and put them in a second compartment.
