Karen walks through how to use one type of decoder in a circuit, a BCD to 7-segment. While this circuit would typically use a microcontroller to provide the four necessary input signals, Karen’s circuit uses 4 switches to allow the user to manually input the BCD number. This circuit is helpful for practicing counting in binary as well as learning how to drive a 7-segment display. This circuit uses a common-anode 7-segment LED display that is driven by an SN74LS47N decoder. If you would like to create a circuit using a common-cathode LED display, a 74LS48 decoder could be used and the power would need to be flipped