Method one, installs the bill acceptor and printer 

Player inserts the paper money, and then adds the credit. When they don’t want to play, they can print the score then go to the service desk to get the cash. 

Method two, use the add credit and decrease credit button. 

You hire waiters to serve the roulette machine. Players give waiter cash, waiter has a key to add scores into the roulette machine for the player, after player stopped, if player wins, the waiter return cash to player, then use the key to zero the roulette machine, and lock it. Normally, one waiter serve two roulette machines.