In The Signal by William Powell Frith, a woman sends a signal by waving a white handkerchief.
A digital signal has two or more distinguishable waveforms, in this example, high voltage and low voltages, each of which can be mapped onto a digit. Characteristically, noise can be removed from digital signals provided it is not too extreme.
A binary signal, also known as a logic signal, is a digital signal with two distinguishable levels
Discrete-time signal created from a continuous signal by sampling
Signal transmission using electronic signals

Function that conveys information about a phenomenon.

- Signal

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Device that converts energy from one form to another.

Mechanical transducer

A sensor is a transducer that receives and responds to a signal or stimulus from a physical system. It produces a signal, which represents information about the system, which is used by some type of telemetry, information or control system.



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.

Noise (electronics)

Unwanted disturbance in an electrical signal.

Random fluctuations of voltage in pink noise.

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


Processed, organized and structured data.

Partial map of the Internet, with nodes representing IP addresses
Galactic (including dark) matter distribution in a cubic section of the Universe
Information embedded in an abstract mathematical object with symmetry breaking nucleus
Visual representation of a strange attractor, with converted data of its fractal structure

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).

Estimation theory

Branch of statistics that deals with estimating the values of parameters based on measured empirical data that has a random component.

The normal distribution, a very common probability density, useful because of the central limit theorem.

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

Data communication

Transfer and reception of data in the form of a digital bitstream or a digitized analog signal over a point-to-point or point-to-multipoint communication channel.

Some of the different types of data.

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

Signaling (telecommunications)

In The Signal by William Powell Frith, a woman sends a signal by waving a white handkerchief.

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


Telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly.

An old rotary dial telephone
AT&T push button telephone made by Western Electric, model 2500 DMG black, 1980
Alexander Graham Bell's Telephone Patent Drawing
Replica of the telettrofono, invented by Antonio Meucci and credited by several sources as the first telephone.
Bell placing the first New York to Chicago telephone call in 1892
Reis's telephone
Bell's first telephone transmitter, ca. 1876, reenacted 50 years later
Acoustic telephone ad, The Consolidated Telephone Co., Jersey City, New Jersey, 1886
1896 telephone from Sweden
Wooden wall telephone with a hand-cranked magneto generator
An IP desktop telephone attached to a computer network, with touch-tone dialing
Fixed telephone lines per 100 inhabitants 1997–2007
Ericsson DBH 1001 (ca. 1931), the first combined telephone made with a Bakelite housing and handset.
Telephone used by American soldiers (WWII, Minalin, Pampanga, Philippines)
Modern sound-powered emergency telephone
One type of mobile phone, called a cell phone

A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user.

Analog signal

Any continuous signal representing some other quantity, i.e., analogous to another quantity.

Discrete sampled signal

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

Electronic engineering

Sub-discipline of electrical engineering which emerged in the early 20th century and is distinguished by the additional use of active components such as semiconductor devices to amplify and control electric current flow.

Printed circuit board

Electronic signal processing deals with the analysis and manipulation of signals.