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In a transistor, that small input current does not produce a large output current, it controls a large output curent.Depending on the exact specifications, changes in that small input can turn the main current on or off (as,in a logic gate), or fluctuations in the input can cause analogous fluctuations in the larger output (as in a music amplifier).But in all cases, the output is slightly less than the input, that lost energy being given up as heat; which is why equipment using them gets hot (or at least warm). Many applications require heat-sinks to deal with the lost energy.Transistors, and all the members of the semiconductor family are more efficient than the vacuum tube which did the same jobs. But none of them are perfect, and they all output less energy than their total input.

George Boole set forth his rules for what would become known as Boolean Algebra in his first book The Mathematical Analysis of Logic (1847). Boolean algebra is the branch of algebra in which the values of the variables are True and False, usually denoted 1 and 0 respectively. This is why almost all computers operate using binary arithmetic. The three basic logic operations are AND, OR, and NOT.Both relays and semiconductor logic gates can perform these three basic operations of Boolean algebra.A relay is an electrically operated switch. Traditional relays have an electromagnet, which when energized, causes one or more electrical contacts to close (or sometimes open). One of the features of electromechanical relays is that the outputs are completely isolated from the input, thus a small AC or DC voltage can control the switching of hundreds of volts and/or amperes, either AC or DC. An AC relay can switch DC voltages and vice-versa.In the diagram below, the contacts A and B are other relays. The first illustrates an AND gate, and the second, an OR gate.A NOT gate is implemented in a relay when a contact is normally closed and opens when the relay is energized.Relays were widely used for doing telephone switching up until the 1960’s, when they began to be replaced by electronic switches. Telephone relays typically used -48VDC.When the outputs of one relay are used to control additional relays, complex logic circuits can be developed. Here is a circuit out of the book The Design of Switching Circuits, written by members of the technical staff at Bell Labs in 1951:The Z3, the world's first working programmable digital computer, was completed in 1941 and used 2200 relays. It was used by the German Aircraft Research Institute to perform statistical analyses of wing flutter.The first electronic digital computers, such as ENIAC (1946), used vacuum tubes as logic gates. Vacuum tube computers dominated until the late 1950’s.The first semiconductor logic gates used discrete transistors, such as these circuits using bipolar transistors:Because the transistor by nature is inverting, the circuits implemented NAND (NOT AND) and NOR (NOT OR) instead of AND and OR.Most digital circuitry today uses CMOS transistors, such as this NAND gate:Here are some individual TTL (transistor-transistor logic) gates in a portion of the schematic of the Apple ][ computer (1975); I have labeled some of them (NOR, AND, OR):Semiconductor logic is of course much faster than relays, on the order of six or more orders of magnitude (typically nanoseconds for various semiconductor families, vs milliseconds for relays).Relays, used as logic switches have a very high fanout, meaning one relay contact can drive many other relay coils. Semiconductor gates are more limited, to about six gates for CMOS, and 10 for TTL.Relays take a lot of power compared to semiconductor gates — tens or hundreds of milliamperes, thousands of times more than a semiconductor gate. Except for latching relays, relays always draw current when on. In contrast, CMOS gates only draw power when they are switching. Relays operate at slighter higher voltages than semiconductor gates — typically 5V to 12V for relays, and 1.8V to 5V for logic gates.Relays are much much larger than a logic gate. Some of today’s microprocessors have billions of transistors in them.Finally, electromechanical relays make a sound when they switch. Semiconductor gates don’t.

I’ve lived in the Bay Area all my life, and I’ve seen a bunch of changes, but the two (2) primary reasons I’ve considered leaving are cost and people’s attitudes.The cost issue is obvious. When the aerospace industry first came in the late 50’s/early 60’s, they brought the first wave of people and prosperity to the region. Before that, the area was mainly agricultural, with heavy industries limited to the San Francisco area (e.g., shipping). The first semiconductor fabrication plants brought the second wave in the late 60’s/early 70’s, followed by other types of computer hardware. Finally, the software and internet companies provided the latest boom in the late 90’s and today.With each of these economic booms came more people and more money. Usually, this is good for a region. Almost any region would love to have the growth that we’ve had over the past 50 years. I would say the last ten years have been the worst from a cost standpoint. With the hyper-inflated valuations of the internet companies, and the competitive salaries of the labor pool, the costs of housing have gone through the roof. It’s nearly impossible for a family with two income earners to buy a house in the Bay Area these days without loans from family members for a downpayment and a bit of luck. Most people are just one or two layoffs away from losing everything in a downturn.The attitude issue is probably more of an issue to me than the cost issue. With all the money floating through the value and San Francisco, there is an air of entitlement with people. More expensive cars, bigger houses, expensive meals, all without putting much back into the community. The income disparity has become huge between those working in tech and those who don’t. I witnessed so much disrespect for service people on a daily basis, it’s embarrassing.I once said to a younger co-worker, “I feel sorry for the security staff having to sit there all day and night.” Her response: “I don’t. It’s their jobs. They're lucky we employ them.” (I shook my head in disbelief). Ask any Lyft or Uber driver in San Francisco, many who drive two or more hours in from the suburbs to drive around SF for hours, how they are treated. It has become a ‘have and have-not’ place.I won't say money has ruined the place, but this isn’t the community of old. The Bay Area is now more like Manhattan, a transient place where people come, make their money, and often leave.It’s sad, and it saddens me that I might have to leave the place where I grew up because of it.