Slots Machines Payout

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There are dozens of different payout systems used in slot machines. In three of the simplest designs, a jackpot is detected by measuring the depth of notches in the discs that drive the reels. For simplicity's sake, we'll look at this sort of payout technique in a bare-bones slot machine. The machine only accepts three kind of coin, and there is only three winning combination of images. 　

When you put a coin in this machine, it falls in to a transparent case. The bottom of the case is a movable shutter that is connected to a metal linkage, as you can see in the diagram. Normally, the linkage holds the shutter closed. But when the machine hits the jackpot, the third stopper shifts the linkage up, opening the shutter so the coins fall out of the machine.

Each of the two discs has notches for each stop position of the reel. The notch for the jackpot stop is deeper than the other stops. Consequently, when the first reel lands on the jackpot stop, the first stopper moves farther to the left than it would for any other stopper. If the second reel stops on the jackpot as well, the second stopper also moves farther left. Same goes for the third reel and stopper.

But if only the second reel stops on the jackpot, the second stopper won't move all the way in to the notch. The first stopper has a catch that keeps the second stopper from moving past it. The second stopper, in turn, has a catch that holds the third stopper back. For the third stopper to lock all the way in to the jackpot notch, then, the first and second reels would must have landed on the jackpot picture. When this happens, the shutter opens to dump all of the coins that have been played since the last jackpot.

In another popular technique used in some electrical machines, the discs have a series of metal contacts attached to them. When the reels stop, three of the contacts engages a stationary contact wired to a circuit board. In this way, every stop on each reel will close a different switch in the electrical technique. Sure combinations of closed switches (jackpot winners) will configure the machine's electrical circuit to operate the payout mechanism.
Typically, slot machines will have more elaborate versions of this design in order to pay out partially on sure combinations of images and pay out on the jackpot combination.

A more advanced technique uses photoelectric cells (also known as photo diodes), devices that generate a current when exposed to light, to detect the position. In this technique, a series of holes are drilled through the rotating discs, all around their outer edges. The photo diode is positioned on three side of the disc, as well as a light source is positioned on the other side. As the disc turns, the light shines through the holes onto the photo diode. The pattern of holes in the disc causes the photo diode to generate a similar pattern of pulses of electricity. Based on this pattern, an electronic circuit can select the position of the reel.

Historically 15 years, electric machines and fully mechanical machines have both been eclipsed by computerized machines. In the next section, we'll see how these modern slots work.