An analog signal or analogue signal is any continuous-time signal representing some other quantity, i.e., analogous to another quantity. For example, in an analog audio signal, the instantaneous signal voltage varies continuously with the pressure of the sound waves.
Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog signal.
Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broadcast television, in which the television signal is transmitted over-the-air by radio waves and received by a television antenna ; or satellite television, in which the television signal is transmitted over-the-air by radio waves from a communications satellite and received by a satellite dish on the roof. FM radio programming, high-speed Internet, telephone services, and similar non-television services may also be provided through these cables. Analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation.
Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio in contrast to the narrower format (4:3) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a separate signal called the modulation signal that typically contains information to be transmitted. For example, the modulation signal might be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing a sequence of binary digits, a bitstream from a computer.
In telecommunications and computer networking, multiplexing is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource – a physical transmission medium. For example, in telecommunications, several telephone calls may be carried using one wire. Multiplexing originated in telegraphy in the 1870s, and is now widely applied in communications. In telephony, George Owen Squier is credited with the development of telephone carrier multiplexing in 1910.
Data communication, including data transmission and data reception, is the transfer of data, transmitted and received over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibers, wireless communication using radio spectrum, storage media and computer buses. The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal.
Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samples are taken 44,100 times per second, each with 16-bit sample depth. Digital audio is also the name for the entire technology of sound recording and reproduction using audio signals that have been encoded in digital form. Following significant advances in digital audio technology during the 1970s and 1980s, it gradually replaced analog audio technology in many areas of audio engineering, record production and telecommunications in the 1990s and 2000s.
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several senders to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.
Terrestrial television or over-the-air television (OTA) is a type of television broadcasting in which the content is transmitted via radio waves from the terrestrial (Earth-based) transmitter of a TV station to a TV receiver having an antenna. The term terrestrial is more common in Europe and Latin America, while in Canada and the United States it is called over-the-air or simply broadcast. This type of TV broadcast is distinguished from newer technologies, such as satellite television, in which the signal is transmitted to the receiver from an overhead satellite; cable television, in which the signal is carried to the receiver through a cable; and Internet Protocol television, in which the signal is received over an Internet stream or on a network utilizing the Internet Protocol. Terrestrial television stations broadcast on television channels with frequencies between about 52 and 600 MHz in the VHF and UHF bands. Since radio waves in these bands travel by line of sight, reception is generally limited by the visual horizon to distances of 64–97 kilometres (40–60 mi), although under better conditions and with tropospheric ducting, signals can sometimes be received hundreds of kilometers distant.
Digital cable is the distribution of cable television using digital data and video compression. The technology was first developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previous analog-based cable by the mid 2010s. During the late 2000s, broadcast television converted to the digital HDTV standard, which was incompatible with existing analog cable systems.
Iowa PBS, formerly Iowa Public Television (IPTV), is a network of Public Broadcasting Service (PBS) member stations in the U.S. state of Iowa. It is operated by the Iowa Public Broadcasting Board, an agency of the state education department which holds the licenses for all the PBS member stations in the state. Iowa PBS' headquarters are located at 6450 Corporate Drive in Johnston, Iowa, a suburb of Des Moines.
Alabama Public Television (APT) is a state network of PBS member television stations serving the U.S. state of Alabama. It is operated by the Alabama Educational Television Commission (AETC), an agency of the Alabama state government which holds the licenses for all of the PBS member stations licensed in the state. The broadcast signals of the nine stations cover almost all of the state, as well as parts of Florida, Georgia, Mississippi and Tennessee. The network produces public affairs, cultural, natural history, and documentary programming; broadcast and online education programs for classroom use and teacher professional development; and electronic field trips serving K-12 students.
HD Radio (HDR) is a trademark for an in-band on-channel (IBOC) digital radio broadcast technology. HD radio generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used primarily by AM and FM radio stations in the United States, U.S. Virgin Islands, Canada, Mexico and the Philippines, with a few implementations outside North America.
WFNA is a television station licensed to Gulf Shores, Alabama, United States, serving as the CW outlet for southwest Alabama and northwest Florida. It is owned and operated by network majority owner Nexstar Media Group alongside Mobile-licensed CBS affiliate WKRG-TV. The two stations share studios with several radio stations owned by iHeartMedia on Broadcast Drive in southwest Mobile; WFNA's transmitter is located in unincorporated Baldwin County near Spanish Fort, Alabama.
South Dakota Public Broadcasting (SDPB) is a network of non-commercial educational television and radio stations serving the U.S. state of South Dakota. The stations are operated by the South Dakota Bureau of Information and Telecommunication, an agency of the state government which holds the licenses for all of the PBS and NPR member stations licensed in South Dakota except KRSD in Sioux Falls, which is owned and run by Minnesota Public Radio, and KAUR in Sioux Falls, which is owned by Augustana University and operated by MPR. SDPB has studios and offices in Rapid City and Sioux Falls with headquarters being located in the Al Neuharth Media Center on the campus of the University of South Dakota in Vermillion.
Nebraska Public Media, formerly Nebraska Educational Telecommunications (NET), is a state network of public radio and television stations in the U.S. state of Nebraska. It is operated by the Nebraska Educational Telecommunications Commission (NETC). The television stations are all members of the Public Broadcasting Service (PBS), while the radio stations are members of National Public Radio (NPR).
Mississippi Public Broadcasting (MPB) is the public broadcasting network serving the U.S. state of Mississippi. It is owned by the Mississippi Authority for Educational Television (MAET), an agency of the state government that holds the licenses for all of the PBS and NPR member stations in the state. MPB's headquarters is located on Ridgewood Road in northeast Jackson. The public broadcaster was established as Mississippi Educational Television.
An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals, or a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper limits of human hearing. Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal back into sound.
Analog passthrough is a feature found on some digital-to-analog television converter boxes. Boxes without the analog passthrough feature only allow older, analog-only TVs to view digital TV. Those with analog pass-through allow both digital and analog television to be viewed on older TVs.
