RF is the type of signal that comes through the air by antenna or through a cable TV connection. In standard-definition broadcast and analogue cable, a composite video signal and accompanying audio are mixed at the transmitting end with high-frequency radio waves and are broadcast through the air or distributed through a cable system. RF is used as a distribution medium because it propagates through the air very well, making it suitable for over-the-air broadcast. As many video signals can be modulated at different frequencies, it is possible to have many ‘channels’ available simultaneously without them interfering with one another.

Analogue equipment is being replaced by digital equipment and is expected to eventually be phased out. But some analogue equipment is still used in industry and in-home theatre applications.

Composite video is a single signal which carries both the chrominance (colour) and luminance (brightness) components of a video signal, along with sync information, on a single wire. Unlike an RF signal, a composite video signal does not need to be demodulated to be understood by a video display. Composite video signals do not carry any audio content. This must be handled separately.

S-video technology transmits standard-definition video with 480 pixels or 576 pixels resolution. S-video cables have a variety of uses, including connecting computers, TVs, DVD players, video cameras, and VCRs. 

S-video is an improvement over composite video, which carries all the video data (including brightness and color information) in one signal over one wire. S-video carries brightness and color information as two separate signals over two wires. Because of this separation, video transferred by S-video is of higher quality than composite video. 

Component video is an analog video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video (CAV) information that is transmitted or stored as three separate signals. Component video can be contrasted with composite video in which all the video information is combined into a single signal that is used in analog television. Like composite, component-video cables do not carry audio and are often paired with audio cables. Similar to s-video, which requires two signal-carrying wires instead of one, component video requires three signal-carrying wires to convey the whole signal.

The original ‘component video’ was RGB, which appears in three principal varieties, each requiring a different number of connections:

• The most common type is RGBHV, with five lines: one for red, one for green, one for blue, one for the horizontal sync and one for the vertical sync. RGBHV is the standard used in VGA and other analogue PC computer monitors.

• RGBS has four connections and differs from RGBHV by having the vertical and horizontal sync combined on a single channel.

• RGsB, or ‘sync-on-green’ places the sync information on the green channel.  Although this is similar to Y/Pb/Pr component video they are not compatible.

DVI and its several flavours: DVI-D, DVI-A, DVI-I.   

DVI is somewhat confusing because the term is identified both with more than one signal type and more than one connector type.   

DVI-A is nothing but RGBHV in a strange connector and isn't digital at all.   

DVI-I isn't really a signal type but refers to a connector type which combines DVI-A and DVI-D.   

DVI-D is a parallel digital standard: a nasty little tangle of wires in a nasty little plug which consists of up to seven balanced lines (all other common video standards are run unbalanced) carrying the video itself, and five miscellaneous conductors carrying other information. Because this is a digital rather than an analogue signal, it can only be converted to another format through a device that is equipped to decode the digital bitstream and render it in analogue form.

HDMI is similar to DVI and is a standard intended to be backward compatible with DVI and employing the same encoding/decoding scheme.

SDI is serial digital video. Unlike DVI, it is run in an unbalanced line. It is used primarily in professional production environments.

Both analog and digital signals carry information. The difference lies in how signals are encoded. In analog technology, waves or signals are stored in the original form, as in the case of an analog recorder where signals are recorded in the tape directly from the microphone. However, in digital technology, waves or signals are sampled at intervals and then converted into numbers before being stored in a digital device. 

Signals that are digitally transmitted require less bandwidth than analog transmitted signals. Moreover, as data is stored in the form of numbers in digital technology, it makes it compact, compressible and easy to process via Digital Signal Processors (DSPs). 

In analog technology, signals are easy to synchronize with smaller bandwidth. Another advantage is that they are easy to process and allow an infinite range of values to be stored. However, a major con of analog signals is that they produce unwanted noise and disturbance in the transmitted data.