![]() ![]() While absent of moving parts, their filaments only worked so long before burning out, and their sealed-glass construction was prone to other means of failure. Vacuum tubes were developed in parallel with light bulbs throughout the 19th century and were first used in an amplifying circuit in 1906. Rather than relying on a magnetic switch, these tubes relied on the “thermionic effect” and resembled dim light bulbs. ![]() The successor to the relay was the vacuum tube. On top of that, relays have moving parts, so they are prone to breaking. For this, relay computers need extensive cooling. The problem with relays is that their electromagnets consume a lot of power, and all that wasted energy turns into heat. Notable relay computers included the Z1 through Z3 (1938-1941) and the Harvard Marks I and II (19). While relays have been used since the discovery of the electromagnet in 1824 - particularly by the 1837 invention of the telegraph - they would not be used for computation until the 20th century. While this method of information storage has taken a back seat to magnetic and optical media, it is still important to some modern computer operations such as cache. Through looping signals backwards, certain kinds of memory are made possible by signal-triggered switches as well. All calculators and computers achieve their mystical power through this method. The only limit to our computing power is how many signal-triggered switches we can use. Similar circuits can be constructed for all sorts of calculations, including addition, subtraction, multiplication, division, conversion between binary (base 2) and decimal (base 10), and so on. ![]() Understanding that XOR behavior is what enables us to "carry the 10" when doing addition, it becomes clear why signal-triggered switches are so vital to computation. "Boolean XOR" switch (Image credit: Robert Coolman) ![]()
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