[add image: circuit of two diodes/switches with inputs A, B, resistor R, +6 V supply and LED (Y)] The LED glows when the voltage across it is high. From the circuit, the truth table is: A = 0, B = 0 → Y = 1 A = 0, B = 1 → Y = 1 A = 1, B = 0 → Y = 1 A = 1, B = 1 → Y = 0 This is the output of a NAND gate.