What does the term PLC stand for?

CDs reproduce 44,100 samples per second. Which has a maximum frequency reproduction of 22,050 Hz, or just a hair past the upper limit of human hearing. In this way CDs can theoretically reproduce any frequency in the human hearing range.

The squirrel cage motor is the only one without any connection to the armature.

A chip found in alomst every microprocessor...

The flyback is usually connected to the system that pulls the electron beam across the screen in one direction to 'paint' a line of the image and then returns in the other direction much faster.

"Noise figure" is one critical parameter for determining the "quality" of a low-noise, small-signal, amplifier, and perhaps more importantly, the sensitivity of the overall receiver system. It is especially important for VHF (very high frequency) - and higher frequency - designs where most of the undesired "noise" (noise that masks or overpowers the desired signals) is generated internal to the electronics itself. In HF (high frequency) applications, atmospheric noise plays a much larger role in determining overall useful sensitivity, so a circuit's "noise figure" is less important.

Neon lighting runs at a high voltage, typically above 1000 Volts. A fireman's switch protects a fireman from receiving a shock when a water jet is sprayed onto the installation. The switches are red, and mounted in a conspicuous position. (This is specified by IEE Regulations (Europe), SANS (South Africa), UK Electricity regulations and many Asian countries. I am unable to confirm other countries' requirements, so feel free to let me know.)