A poker table reader is a sophisticated device that allows you to read marked cards at a distance as small as an inch. Poker tournaments and TV productions use it to keep track of hands in a game. The device is powered by an infrared (IR) sensor that can see the markings on the cards. The device then sends this information to a computer, which can display it.
To ensure that the card of a player is not being recorded, there is a camera on the device that can detect the infrared light coming from the marks. This camera is hidden on a side of the gadget that appears solid, but is actually made from IR passband material that allows IR lights to pass. In addition to the IR sensor, the device also has three hidden IR LEDs that illuminate the cards. This is why pointing a phone camera at the device will reveal its three LEDs.
The IR sensors are connected to a mother board that acts as the brain for the device. The motherboard translates the incoming IR signals and sends them to a computer installed in the table that can display the results on a screen. The computer can display real-time information or delayed information on the cards being played.
This type of technology changes the behavior of players. It forces the players to hold their cards for a moment over the reading zone, and that is not always possible.