Thermistor A transducer which converts temperature (heat) to resistance (an electrical property).
Loudspeaker A transducer which converts electrical energy to sound.
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).
Zener diode A zener diode can be used to maintain a fixed voltage.