Diode A device which allows current to flow in only one direction.
Microphone A transducer which converts sound to electrical energy.
An AND gate can have two or more inputs. The output of an AND gate is true when all its inputs are true.
Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low, 0V, off). For more information please see the page on logic gates. There are two sets of symbols: traditional and IEC (International Electrotechnical Commission).