No Peek 21 Blackjack Electronic Card Reader with power supply. Dimensions: 8 in × 6 in × 4 in The basic purpose of the No Peek 21 reader is to enable the dealer to determinewhether or not the value of his first two cards is twenty-one (21) without having tobend and look at his hole card. This eliminates the need for the dealer to know theexact value of his cards until it is time for the dealer to turn his hand over. Specific cards needed for this reader: In order for the No Peek 21 device to operate properly it must be used in conjunction with playing cards which have been specially marked for the use with the No Peek 21 device. The markings on the cards consists of black hexagons placed on diagonal corners on all ten value cards and on the aces. On the aces the markings are placed on the opposite corners from where they are placed on the ten value cards. How it works: When the dealer has either an ace or a ten value card as his face card, he inserts the two cards into the No Peek 21 reader which senses the value of the bottom "hole card" and triggers either a red or green light depending on whether the value of the two cards is twenty-one (21) or less. If the value of the two cards is twenty-one (21) the red light on the top of the reader is activated. If the value of the two cards are less than twenty-one (21) the green light on the top of the reader is activated. Its power source is hard-wire standard AC-DC adapter power supply (100-240V AC current) . The device draws current only when the cards are inserted in it activating the sensor switch.