Ask the Slot Expert: When does a Class II slot machine stop the bingo drawing?

Question: Last week I went to a casino on Macau (I live in Hong Kong) to play 50 Lions. I got 24 lions mixed with diamonds on all lines. I love the game.

I know that Las Vegas has regulations that the payback rate should be at least 90%. Do you have any information about the payback rate for slot machines in Macau?

Answer: On 50 Lions, the lion symbol is the highest-paying symbol (no surprise there). The diamond is wild, so you in effect filled the screen with lions. That must have been quite a large payout.

I was able to find a document called EGM Technical Standards Version 1.1 for Macau online. EGM stands for Electronic Gaming Machine. In the U.S. we usually use EGD (Electronic Gaming Device). Both designations include slot, video poker, video blackjack, video keno -- just about every electronic gaming machine. Fortunately, only the department titles in the document are in Portuguese and Chinese; the text is in English.

Section 4.7 is Return to Player. Item 1 covers the minimum return. The text is a bit confusing.

A game must have a theoretical/estimated statistical expectation that the minimum player return (RTP) of the game will be greater than or equal to [MINRTP]. The minimum percentage must be met when playing at the lowest percentage available. If no minimum RTP is prescribed by regulation for the time being, it shall be taken to be 80%.

Item 2 is almost identical for the maximum.

A game must have a theoretical/estimated statistical expectation that the maximum player return (RTP) of the game will be less than or equal to [MAXRTP]. If no maximum RTP is prescribed by regulation for the time being, it shall be taken to be 98%.

What are [MINRTP] and [MAXRTP]? Beats me. They aren't defined or referred to anywhere else in the document. They look like placeholders that were supposed to be replaced with actual numbers before the document was released.

I couldn't find any slot regulations for Macau online, but it's safe to assume that the paybacks are between 80% and 98%. I found a few articles and papers written before the standards document went into effect, and they said that the casino operators confirmed a top payback of 95%.

It's dangerous to draw any conclusions from anecdotal evidence, but posts online from people who have played in both the U.S. and Macau think that the slots in the U.S. pay back more.

By the way, the regulations in Nevada require a payback of at least 75%, not 90%. Competition, fortunately, keeps actual minimum in the field somewhere in the 80s for the lowest-paying machines.

Question: On a Class II slot machine, how does the RNG simulating the bingo drawing know when to stop? If I get issued a digital bingo card and push the spin button so the RNG starts the ball-picking process, how does it know if I win or lose unless it knows when to stop dropping balls? As the only card in play, would it not just keep calling numbers until someone wins? Or does it call a fixed number of balls?

Answer: The process of determining the outcome of a spin on a Class II slot machine is much more complicated than that on a machine with an RNG and I'll admit that I don't know all the details.

Keep in mind that there is no RNG in a Class II slot machine. The bingo drawing takes place on a central server.

When you press the spin button, the server is notified that you want to participate in the next drawing. The server does not proceed with the drawing until a minimum number of players have joined the drawing. The minimum could be two. I have heard of players playing in the wee hours having to wait for their spins to be resolved.

The server proceeds with the drawing once it has the minimum number of players required. The server draws numbers until at least one player has a bingo. (Some systems may also stop after a certain number of balls have been drawn even if no one has achieved a bingo.) Each machine then compares the pattern covered on its card with the table of winning patterns. If the pattern is a winning pattern, it then spins the reels to the corresponding reel combination and pays the amount won. Note that the winning patterns aren't necessarily the typical winning bingo patterns. A winning pattern can be any pattern on the card.

Frank Scoblete and I consulted on a machine that used this method to determine what was won many (many) years ago. Another method to determine how much was won is to have the server choose a winning amount from its pool of winning amounts and tell each machine that had a bingo how much was won. Each machine then displays a reel combination corresponding to the amount won.