The slot machine is one of the few pieces of nineteenth-century engineering still in daily commercial use, though almost nothing about the modern version is mechanical. Tracing how it got from a cast-iron cabinet with three physical reels to a game with 117,649 ways to win explains a surprising amount about why current games behave the way they do — particularly the single patent, filed in 1984, that made large jackpots mathematically possible.
Most of what players think of as recent innovation is considerably older than it looks. Most of what looks traditional was invented for regulatory reasons that no longer exist. The lineage is easy enough to trace in a modern lobby if you sort by release date and mechanic — filters available on platforms that catalogue titles by format rather than by theme, including https://caswinoaustralia.com and others that expose provider and mechanic data directly — because the design generations remain clearly visible in the games still running today.
The mechanical era
The direct ancestor appeared in Brooklyn in 1891, when Sittman and Pitt built a machine with five drums holding fifty playing cards. Players inserted a nickel, pulled a lever, and were paid by the bar they were standing in — a free drink for a pair of kings, a cigar for a flush. The machine could not pay out automatically because the number of possible poker hands made an automatic payout mechanism impractical.
Charles Fey solved that in San Francisco around 1895 by cutting the problem down. His Liberty Bell used three reels with five symbols each, giving 125 possible combinations — few enough that a mechanism could detect a winning line and release coins. That reduction from cards to symbols, made purely for engineering reasons, defined the format for the next century.
The fruit symbols arrived around 1907 with Herbert Mills’s Operator Bell, and they exist for legal reasons. With gambling restricted across much of the United States, machines were reframed as vending devices dispensing chewing gum, and the symbols represented flavours — cherry, lemon, plum. The bar symbol still found on modern reels is a stylised gum packet. Australia’s own tradition ran on a parallel track: poker machines were legalised in New South Wales clubs in 1953, the same year Aristocrat was founded, and “pokies” retained the card-based naming long after the reels stopped showing cards.
Electromechanics and the hopper
Bally’s Money Honey, released in 1963, was the first machine with a fully electromechanical payout system and a hopper capable of dispensing up to 500 coins without an attendant. The lever survived, but only as a habit — the machine no longer needed it.
That change mattered more than it sounds. Automatic payout of larger sums meant machines could offer prizes worth queuing for, and the format shifted from a bar-top novelty toward a primary attraction.
The first video slot followed in 1976, built by Fortune Coin Co and installed at the Las Vegas Hilton after regulatory approval in 1978. Players distrusted it initially for an understandable reason: with no physical reels, there was nothing visible to verify.
The 1984 patent that changed the maths
This is the pivotal moment, and it is almost never discussed outside the industry.
On a genuinely mechanical three-reel machine, the top prize is limited by physics. With 22 stops per reel, there are 10,648 combinations, so the largest payout that keeps the game profitable is modest. Adding reels or stops makes cabinets physically unwieldy.
Inge Telnaes patented a solution in 1984: map a large number of virtual positions onto each physical reel stop, so that a computer selects from thousands of virtual outcomes and then displays a corresponding physical position. The reels became a display of a result, not the generator of it.
The consequence was that jackpot odds and reel appearance became fully independent variables. Machines could offer prizes of a million to one while still showing three spinning reels. The patent was acquired by IGT, and every modern slot — physical or online — descends from that principle. It is also the origin of the near-miss effect, since virtual mapping allows the symbol just above the payline to appear far more often than a genuinely random reel would produce.
The timeline
| Year | Development | Why it mattered |
|---|---|---|
| 1891 | Sittman and Pitt card machine | First reel-based gambling device; paid manually |
| 1895 | Fey’s Liberty Bell | Three reels, automatic payout |
| 1907 | Operator Bell, fruit symbols | Legal workaround that became visual convention |
| 1953 | Poker machines legalised in NSW clubs | Foundation of the Australian pokies tradition |
| 1963 | Bally Money Honey | Electromechanical hopper, larger automatic payouts |
| 1976 | First video slot | Screen replaces physical reels |
| 1984 | Telnaes virtual reel patent | Made large jackpots mathematically possible |
| 1996 | Second-screen bonus rounds | Introduced the feature round as a format |
| 1996–98 | First online casinos and progressive jackpots | Pooling across operators |
| 2016 | Megaways engine | Variable ways-to-win, up to 117,649 |
| 2020 | Flash discontinued, HTML5 standard | Full mobile parity |
Online, then mobile
The first online casinos launched in the mid-1990s, and the first pooled online progressive jackpot followed in 1998. The significance was structural rather than technical: a jackpot fed by players across many operators simultaneously could reach sizes no single venue could fund.
The mobile transition through the 2010s was more consequential for design than for maths. Flash gave way to HTML5, which meant games rendered identically on any device, and studios began building portrait-first. Session lengths shortened, features were compressed, and the industry reorganised around a phone screen.
Big Time Gaming’s Megaways engine, introduced in 2016, was the most significant mathematical innovation since 1984 — variable symbol counts per reel producing up to 117,649 ways to win on a single spin, and a volatility profile the older formats could not reach.
What actually changed, and what did not
- The reels stopped being the game in 1984. Everything visible on screen since then is a presentation of a result decided by a random number generator.
- The lever became decorative in 1963 and was gone entirely by the online era.
- Fruit symbols are a legal artefact of American anti-gambling law, preserved for over a century by convention alone.
- Payout ceilings rose by orders of magnitude — from a few hundred coins to caps of 50,000x the stake.
- The mathematical structure did not change. A house edge built into the payout schedule has been the operating principle since 1895; only its precision has improved.
- Verification moved from visible to certified. Physical reels could be inspected; virtual ones are audited by testing laboratories instead, which is why certification became necessary the moment the reels stopped mattering.
That last point is the through-line. The entire history is a progression from a machine whose fairness you could see to a machine whose fairness is a matter of documentation — which is why knowing how to check the documentation is now the practical equivalent of examining the reels.
A closing note that belongs in any honest piece on this subject: every version of this machine across 130 years has been built to return less than it takes, and the technology changed the presentation rather than the principle. Set a budget you are entirely comfortable losing, decide your stop point in advance, and step away when you reach it. Gambling is for adults 18+ only, and free support services operate in every Australian state.