An integrated circuit or other device whose inputs and outputs represent Boolean or binary values as voltages (TTL uses 0V for False or 0, +5V for True or 1). Different gates implement different Boolean functions: AND, OR, NAND, NOR (these may take two or more inputs) NOT (one input), XOR (two inputs). NOT, NAND and NOR are often constructed from single transistors and the other gates made from combinations of these basic ones. These functions are all combinatorial logic functions, i.e. their outputs depend only on their inputs and there is no internal state. Gates with state, such as latches and flip-flops, are constructed by feeding some of their outputs back to their inputs.