Analog

An electronic analog signal is a continuous electrical voltage or current waveform that varies smoothly and continuously over time.  In electronic systems, analog signals are used to represent real world quantities, such as sound, temperature, light, or other physical phenomena.  These signals are characterized by an infinite range of possible values within a given range.

Key Points about Electronic Analog Signals

Continuous Variation  -  Analog signals can take on any value within a specified range, and they change smoothly and continuously.  This is in contrast to digital signals, which are discrete and can only take on specific values.
Representation of Physical Phenomena  -  Electronic analog signals are often used to represent physical quantities.  For example, in audio systems, an analog electrical signal can represent variations in air pressure (sound).  In temperature sensors, analog signals may represent changes in temperature.
Waveform Characteristics  -  Analog signals are typically described by their waveform characteristics, such as amplitude, frequency, and phase.  These characteristics determine how the signal varies over time.
Processing and Transmission  -  Analog signals can be processed using analog circuits, which manipulate the signal in a continuous manner.  They can also be transmitted over analog communication channels, such as analog radio or television broadcasts.
Vulnerability to Noise  -  Analog signals are susceptible to noise and interference, as any small disturbances in the signal can affect the information it carries.  This is one reason why digital signals, which are more resistant to noise, are often preferred in modern communication systems.

Examples of electronic analog signals include the voltage variations in an audio signal coming from a microphone or the continuous voltage changes in an analog sensor measuring light intensity.  While analog signals were prevalent in older electronic systems, many modern applications, especially in communications and data processing, have shifted to digital signals for improved reliability and processing capabilities.