The D'Alembert Strategy is named after the Jean le Rond d'Alembert, a French physician from the 18th century. It is based on the concept that two outcomes with equal chances will occur more or less equal number of times. The basic unit is added or subtracted to the bet based upon the previous bet's result. The bet decreases after a bet is won and increases after the bet is lost. In simple words, while playing bingo if you have won a round, then the D'Alembert Strategy advices that your chances of winning again are less. Hence, you place a low bet.
The difference between Martingale and D' Alembert System is that with the later the bet amount is not doubled once you lose a bet. Hence, the stakes grow slowly, unlike the Martingale System where it grows rapidly.
There is a mistake in one of the assumptions in the D' Alembert System. There is a tiny mistake in the concept of the system. In case you can figure it out, then you will instantly get that this system cannot entirely help in overcoming the house edge. The system supposes that in case the player wins, there is a lesser probability of winning the next spin. Therefore, the system requires the player to bet less. But actually the chance of winning the proceeding spin is equal to losing it. It is neither less nor more. In Roulette, for example, every time the wheel spins, it is a completely independent event. There is no relation between the present spin and the previous spin or the next spin.
Consider that a coin is being flipped. In case a flip brings heads, then there is an equal chance that may again get a head on the next flip. The chance is always a 50 - 50. And there is a chance that the coin may land 10,000 times on the heads before hitting a tails. It may also alternate with every flip.
Even when the D'Alembert System is used for hedging against losses in bingo, it proves to be a faulty system. When you lose a bet on the proceeding spin, the system considers that there is a lesser chance of losing on the proceeding spin. Therefore it requires you to bet more. As with winning, the chance of losing on every spin is the same as winning.