<P> Mobile is when the slot machine is hosted for online gambling and it is usually available for use on a phone, tablet, or other portable device . These are often standalone mobile casino applications but are also found as part of the online casino site . See Mobile gambling . </P> <P> Each machine has a table that lists the number of credits the player will receive if the symbols listed on the pay table line up on the pay line of the machine . Some symbols are wild and can represent many, or all, of the other symbols to complete a winning line . Especially on older machines, the pay table is listed on the face of the machine, usually above and below the area containing the wheels . Most video machines display the pay table when the player presses a "pay table" button or touches "pay table" on the screen; some have the pay table listed on the cabinet as well . </P> <P> Historically, all slot machines used revolving mechanical reels to display and determine results . Although the original slot machine used five reels, simpler, and therefore more reliable, three reel machines quickly became the standard . </P> <P> A problem with three reel machines is that the number of combinations is only cubic--the original slot machine with three physical reels and 10 symbols on each reel had only 10 = 1,000 possible combinations . This limited the manufacturer's ability to offer large jackpots since even the rarest event had a likelihood of 0.1% . The maximum theoretical payout, assuming 100% return to player would be 1000 times the bet, but that would leave no room for other pays, making the machine very high risk, and also quite boring . </P>

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