Analog television in the context of Progressive scan

A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a frame of video on an analog television set (TV), digital raster graphics on a computer monitor, or other phenomena like radar targets. A CRT in a TV is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons.

In CRT TVs and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In modern CRT monitors and TVs the beams are bent by magnetic deflection, using a deflection yoke. Electrostatic deflection is commonly used in oscilloscopes.

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.

A cable channel (sometimes known as a cable network) is a television network available via cable television. Many of the same channels are distributed through satellite television. Alternative terms include non-broadcast channel or programming service, the latter being mainly used in legal contexts. The abbreviation CATV is used in the US for cable television and originally stood for community antenna television, from cable television's origins in 1948; in areas where over-the-air TV reception was limited by distance from transmitters or mountainous terrain, large community antennas were constructed, and cable was run from them to individual homes.

Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. In the 2000s it was represented as 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 (commonly 16:9) 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:

• Digital Video Broadcasting (DVB) uses coded orthogonal frequency-division multiplexing (OFDM) modulation and supports hierarchical transmission. This standard has been adopted in Europe, Africa, Asia and Australia, for a total of approximately 60 countries.
• Advanced Television System Committee (ATSC) standard uses eight-level vestigial sideband (8VSB) for terrestrial broadcasting. This standard has been adopted by 9 countries: the United States, Canada, Mexico, South Korea, Bahamas, Jamaica, the Dominican Republic, Haiti and Suriname.
• Integrated Services Digital Broadcasting (ISDB) is a system designed to provide good reception to fixed receivers and also portable or mobile receivers utilizing OFDM and two-dimensional interleaving. It supports hierarchical transmission of up to three layers and uses MPEG-2 video and Advanced Audio Coding. This standard has been adopted in Japan and the Philippines. ISDB-T International is an adaptation of this standard using H.264/MPEG-4 AVC, which has been adopted in most of South America as well as Botswana and Angola. 1seg (1-segment) is a special form of ISDB. Each channel is further divided into 13 segments. Twelve are allocated for HDTV and the other for narrow-band receivers such as mobile televisions and cell phones.
• Digital Terrestrial Multimedia Broadcast (DTMB) adopts time-domain synchronous (TDS) OFDM technology with a pseudo-random signal frame to serve as the guard interval (GI) of the OFDM block and the training symbol. The DTMB standard has been adopted in China, including Hong Kong and Macau.
• Digital Multimedia Broadcasting (DMB) is a digital radio transmission technology developed and adopted in South Korea as part of the national information technology project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones, laptops and GPS navigation systems.

A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.

Analog AM and FM radio broadcast networks as well as digital broadcast networks can operate in this manner. SFNs are not generally compatible with analog television transmission, since the SFN results in ghosting due to echoes of the same signal.

A television channel, or TV channel, is a terrestrial frequency or allocated number over which a television station or television network is distributed. For example, in North America, channel 2 refers to the terrestrial or cable band of 54 to 60 MHz, with carrier frequencies of 55.25 MHz for NTSC analog video (VSB) and 59.75 MHz for analog audio (FM), or 55.31 MHz for digital ATSC (8VSB). Channels may be shared by many different television stations or cable-distributed channels depending on the location and service provider.

Depending on the multinational bandplan for a given region, analog television channels are typically 6, 7, or 8 MHz in bandwidth, and therefore television channel frequencies vary as well. Channel numbering is also different. Digital terrestrial television channels are the same as their analog predecessors for legacy reasons, however through multiplexing, each physical radio frequency (RF) channel can carry several digital subchannels. On satellites, each transponder normally carries one channel, however multiple small, independent channels can be on one transponder, with some loss of bandwidth due to the need for guard bands between unrelated transmissions. ISDB, used in Japan and Brazil, has a similar segmented mode.

A scan line (also scanline) is one line, or row, in a raster scanning pattern, such as a line of video on a cathode-ray tube (CRT) display of a television set or computer monitor.

On CRT screens the horizontal scan lines are visually discernible, even when viewed from a distance, as alternating colored lines and black lines, especially when a progressive scan signal with below maximum vertical resolution is displayed. This is sometimes used today as a visual effect in computer graphics.

In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.

DACs are commonly used in music players to convert digital data streams into analog audio signals. They are also used in televisions and mobile phones to convert digital video data into analog video signals. These two applications use DACs at opposite ends of the frequency/resolution trade-off. The audio DAC is a low-frequency, high-resolution type, while the video DAC is a high-frequency low- to medium-resolution type.

NTSC (from National Television System Committee) was the first American standard for analog television, published and adopted in 1941. In 1957, the EIA defined NTSC performance standards in EIS-170 (also known as RS-170). In 1961, the color version of NTSC was designated NTSC-M by the CCIR, with the Japanese variant, which used a somewhat different color implementation, designated NTSC-J.

In 1953, a second NTSC standard was adopted, which allowed for color television broadcast compatible with the then existing stock of black-and-white receivers. It was one of three major color formats for analog television, the others being PAL and SECAM. NTSC color was usually associated with the System M; this combination was sometimes called NTSC II. The only other broadcast television system to use NTSC color was the System J. Brazil used System M with PAL color. Vietnam, Cambodia, and Laos used System M with SECAM color. Vietnam later switched to PAL in the early 1990s.

Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 frames) per second, and associated with CCIR analogue broadcast television systems B, D, G, H, I and K. The articles on analogue broadcast television systems further describe frame rates, image resolution, and audio modulation.

PAL video is composite video because luminance (luma, monochrome image) and chrominance (chroma, colour applied to the monochrome image) are transmitted together as one signal. A latter evolution of the standard, PALplus, added support for widescreen broadcasts with no loss of vertical image resolution, while retaining compatibility with existing sets. Almost all of the countries using PAL are currently in the process of conversion, or have already converted transmission standards to DVB, ISDB or DTMB. The PAL designation continues to be used in some non-broadcast contexts, especially regarding console video games where it is referring to the markets other than North America and Japan.

SECAM, also written SÉCAM (French pronunciation: [sekam],Système Électronique Couleur Avec Mémoire, French for electronic colour system with memory), is an analogue colour television system that was used in France, Russia, and some other countries or territories of Europe and Africa. It was one of three major analog colour television standards, the others being PAL and NTSC. Like PAL, a SECAM picture is also made up of 625 interlaced lines and is displayed at a rate of 25 frames per second (except SECAM-M). However, due to the way SECAM processes colour information, it is not compatible with the PAL video format standard. SECAM video is composite video; the luminance (luma, monochrome image) and chrominance (chroma, color applied to the monochrome image) are transmitted together as one signal.

All the countries using SECAM have either converted to Digital Video Broadcasting (DVB), the new pan-European standard for digital television, or are currently in the process of conversion. SECAM remained a major standard into the 2000s.

Broadcast television systems (or terrestrial television systems outside the US and Canada) are the encoding or formatting systems for the transmission and reception of terrestrial television signals.

Analog television systems were standardized by the International Telecommunication Union (ITU) in 1961, with each system designated by a letter (A-N) in combination with the color standard used (NTSC, PAL or SECAM) - for example PAL-B, NTSC-M, etc.). These analog systems for TV broadcasting dominated until the 2000s.

Giovanni Caselli (8 June 1815 – 25 April 1891) was an Italian priest, inventor, and physicist. He studied electricity and magnetism as a child which led to his invention of the pantelegraph (also known as the universal telegraph or all-purpose telegraph), the forerunner of the fax machine. The world's first practical operating facsimile machine ("fax") system put into use was by Caselli. He had worldwide patents on his system. His technology idea was further developed into today's analog television.

Caselli was a student and professor at the University of Florence in Italy. He started a technical journal that explained physics in layman's terms. For his pantelegraph technology he was awarded the Legion of Honor by Napoleon III of France. Parisian scientists and engineers started the Pantelegraph Society to exchange ideas about the pantelegraph and the associated synchronizing apparatus, in order to get the sending and receiving mechanisms to work together properly.