The machines featured three spinning reels with ten symbols on each. The probability of winning on the old machines is easy to compute. They offered 1000 combinations and paid out 750 total prizes, so the house won 250 units. Other small payouts might range from once every 20 plays to once every 500 pays. However, a nice 80 to 1 payout may be set to payoff more often. It may hit every 200 plays (on average, of course). The first thing to remember is that each slot machine has its own list of payoffs and rules. Read the payoffs chart and what it takes to win. Most newer slots have a "menu" or "Game info" button that. A RNG is a computational device designed to generate a series or sequence of numbers or symbols that lack any pattern, thus rendering them random. The first patent for such a device was granted in 1984 to Inge Telnaes. The next spin may be a payoff, but the next 20 spins may not! Slot Psychology. In case you didn't know it, slot machine manufacturers use psychology to set the winning combination percentages. That's why manufacturers like. This works for them because the medium jackpots hit regularly enough to to enjoy, and when they do get an 80-1 or similar payoff, they know it won't hit again for a while and move on to another machine. This percentage is similar to video poker machines, although perfect play of some video poker machines can actually give the player a small edge over the casino, especially when player's club comps are added in. Related Articles Our Expert.