Compact discs, (according to the original CD specifications) hold how many minutes of music?

Phil Zimmermann created the first version of PGP encryption in 1991. Pretty Good Privacy (PGP) is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. PGP is often used for signing, encrypting and decrypting texts, E-mails, files, directories and whole disk partitions to increase the security of e-mail communications.

Useful in tuning and filtering circuits, it blocks DC while passing AC. How much charge a capacitor can store is its capacitance, measured in farads.nn

Electricity is voltage and current. Voltage is electrical pressure, and current is the flow of charged particles. The difference between alternating current (AC) and direct current (DC) is that the electrons in an AC circuit regularly reverse their direction. In a DC circuit electrons always flow in the same direction.

An uninterruptable power supply (UPS) is a backup power supply, such as a battery, that provides emergency power in the event that power is lost from the main supply.

Amplitude modulation was the first type to be used in radio. It works well with HF and morse code.

"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.