Complex sentence: The vacuum tube was the only amplifying device (besides specialized power devices such as the magnetic amplifier and amplidyne) for 40 years, and dominated electronics until 1947, when the first transistor, the BJT, was invented.
Split into simpler sentences: The vacuum tube was the only amplifying device (besides specialized power devices such as the magnetic amplifier and amplidyne) for 40 years. Tubes dominated electronics until 1947, when the first transistor, the BJT, was invented.