A progressive jackpot is exactly what the name says a jackpot that is increased by a percentage of every bet with each game played and is paid out when the highest combination (jackpot) hits on one of the connected slot machines. A number of American companies quickly followed with developing digital displays, after which progressive jackpots became a regular part of every casino floor. As more and more electronics entered the casino industry, slot machines were linked together and in the 1980s the Australian company Aristocrat introduced one of the first linked progressive jackpots on multiple slot machines where the prize was visible on a so-called electronic flip meter. Players appreciated the extra prize and ignored other slots. It soon became apparent that this type of slot machine was much more popular than its counterparts without a jackpot.
At the beginning of the 20th century, the first mechanical slot machines were equipped with a reservoir in which coins accumulated that were paid out in one go when the least common symbols (jackpot 7-7-7) from the pay table were lined up It was the first form of a progressive jackpot.
