Signal

In communication systems, signal processing, and electrical engineering, a signal is a function that "conveys information about the behavior or attributes of some phenomenon".

Signal processing is a subfield of mathematics, information and electrical engineering that concerns the analysis, synthesis, and modification of signals, which are broadly defined as functions conveying "information about the behavior or attributes of some phenomenon", such as sound, images, and biological measurements.

In communication systems, signal processing, and electrical engineering, a signal is a function that "conveys information about the behavior or attributes of some phenomenon".

Information can be encoded into various forms for transmission and interpretation (for example, information may be encoded into a sequence of signs, or transmitted via a signal).

In human engineering, signals are typically provided by a sensor, and often the original form of a signal is converted to another form of energy using a transducer.

Usually a transducer converts a signal in one form of energy to a signal in another.

For example, a microphone converts an acoustic signal to a voltage waveform, and a speaker does the reverse. Sound. Since a sound is a vibration of a medium (such as air), a sound signal associates a pressure value to every value of time and three space coordinates. A sound signal is converted to an electrical signal by a microphone, generating a voltage signal as an analog of the sound signal, making the sound signal available for further signal processing. Sound signals can be sampled at a discrete set of time points; for example, compact discs (CDs) contain discrete signals representing sound, recorded at 44,100 samples per second; each sample contains data for a left and right channel, which may be considered to be a 2-vector signal (since CDs are recorded in stereo). The CD encoding is converted to an electrical signal by reading the information with a laser, converting the sound signal to an optical signal.

A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal.

The prevention of noise is covered in part under the heading of signal integrity.

Signal integrity or SI is a set of measures of the quality of an electrical signal.

The term noise usually means an undesirable random disturbance, but is often extended to include unwanted signals conflicting with the desired signal (such as crosstalk).

In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.

The separation of desired signals from a background is the field of signal recovery, one branch of which is estimation theory, a probabilistic approach to suppressing random disturbances.

Detection theory or signal detection theory is a means to measure the ability to differentiate between information-bearing patterns (called stimulus in living organisms, signal in machines) and random patterns that distract from the information (called noise, consisting of background stimuli and random activity of the detection machine and of the nervous system of the operator).

The separation of desired signals from a background is the field of signal recovery, one branch of which is estimation theory, a probabilistic approach to suppressing random disturbances.

As another example, in electrical communication theory, the measurements which contain information regarding the parameters of interest are often associated with a noisy signal.

Engineering disciplines such as electrical engineering have led the way in the design, study, and implementation of systems involving transmission, storage, and manipulation of information.

The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal.

In telephone networks, signaling, for example common-channel signaling, refers to phone number and other digital control information rather than the actual voice signal.

In telecommunication, signaling is the use of signals for controlling communications.

For example, the words "Mary had a little lamb" might be the message spoken into a telephone.

The transmitter converts the sound waves to electrical signals which are sent through a telephone network to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker.

In communication systems, signal processing, and electrical engineering, a signal is a function that "conveys information about the behavior or attributes of some phenomenon".

Equipment consists of a transmitter, which encodes a message into an optical signal, a communication channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal.

Another important property of a signal is its entropy or information content.

In information theory, information content, self-information, or surprisal of a random variable or signal is the amount of information gained when it is sampled.

In communication systems, signal processing, and electrical engineering, a signal is a function that "conveys information about the behavior or attributes of some phenomenon".

Signal processing deals with the analysis and manipulation of signals.

Two main types of signals encountered in practice are analog and digital.

A digital signal is a signal (in electronic devices a voltage or a current) that is being used to represent data as a sequence of discrete values; at any given time it can only take on one of a finite number of values.

In the latter half of the 20th century, electrical engineering itself separated into several disciplines, specialising in the design and analysis of systems that manipulate physical signals; electronic engineering and computer engineering as examples; while design engineering developed to deal with functional design of user–machine interfaces.

Signal processing deals with the analysis and manipulation of signals.

Discrete-time signals are often referred to as time series in other fields.

A continuous signal or a continuous-time signal is a varying quantity (a signal)

The formal study of the information content of signals is the field of information theory.

Under these constraints, we would like to maximize the rate of information, or the signal, we can communicate over the channel.

Two main types of signals encountered in practice are analog and digital.

The term analog signal usually refers to electrical signals; however, mechanical, pneumatic, hydraulic, human speech, and other systems may also convey or be considered analog signals.

The physical quantity may be a variable electric current or voltage, the intensity, phase or polarization of an optical or other electromagnetic field, acoustic pressure, the magnetization of a magnetic storage media, etcetera.

Poulsen's device recorded a signal on a wire wrapped around a drum.

Sound. Since a sound is a vibration of a medium (such as air), a sound signal associates a pressure value to every value of time and three space coordinates. A sound signal is converted to an electrical signal by a microphone, generating a voltage signal as an analog of the sound signal, making the sound signal available for further signal processing. Sound signals can be sampled at a discrete set of time points; for example, compact discs (CDs) contain discrete signals representing sound, recorded at 44,100 samples per second; each sample contains data for a left and right channel, which may be considered to be a 2-vector signal (since CDs are recorded in stereo). The CD encoding is converted to an electrical signal by reading the information with a laser, converting the sound signal to an optical signal.

The two signals were sent out over separate AM station bands.

Once expressed as an electronic signal, the signal is available for further processing by electrical devices such as electronic amplifiers and electronic filters, and can be transmitted to a remote location by electronic transmitters and received using electronic receivers.

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current).

In an electrical signal, the voltage, current, or frequency of the signal may be varied to represent the information.

This is an electronic instrument which measures the frequency of an applied repetitive electronic signal and displays the result in hertz on a digital display.

Current loop – a signaling system in widespread use for process control

In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors.

The information in a signal is usually accompanied by noise.

In communication systems, noise is an error or undesired random disturbance of a useful information signal.