Complex sentence: Triodes were widely used in consumer electronics until the 1950s, when bipolar junction transistors replaced them; their main remaining use is for high power RF amplifiers in radio transmitters and industrial RF heating devices.
Split into simpler sentences: Triodes were widely used in consumer electronics until the 1950s, when transistors replaced them. Today their main remaining use is for high power RF amplifiers in radio transmitters and industrial RF heating devices.