Analog signals

An Analog signal uses some attribute of the medium to convey the signal's information.

Electrical signals may represent information by changing their voltage, current, frequency, or total charge. Information is converted from some other physical form (like sound, light, temperature, pressure, position) to an electrical signal by a Transducer which converts one type of energy into another

The signals take any value from a given range, and each unique signal value represents different information. Any change in the signal is meaningful, and each level of the signal represents a different level of the phenomenon that it represents.

Another method of conveying an analogue signal is to use modulation. some base carrier signal has one of its properties altered: amplitude modulation (AM) involves altering the amplitude of a sinusoidal voltage waveform by the source information, frequency modulation (FM) changes the frequency. Other techniques, such as phase modulation or changing the phase of the carrier signal

In an analog sound recording, the variation in pressure of a sound striking a microphone creates a corresponding variation in the current passing through it or voltage across it. An increase in the volume of the sound causes the fluctuation of the current or voltage to increase proportionally while keeping the same waveform or shape.

An Aneroid barometer uses the angular position of a needle as the signal to convey the information of changes in atmospheric pressure