Introduction to Television

Television systems can be either monochrome (black and white) or color, and they are quite different, although color must be compatible with monochrome.

Transmission of Pictures

A television system uses one or more television cameras to convert the light energy of a natural moving visible scene, either in a television studio or outdoors, into an electronic signal. Alternatively, the signal may be obtained from a video tape recorder, from telecine machines, or from slide scanners. These last two convert films or photographic slides into appropriate signals.

This signal is usually conveyed by line to a television transmitting station where it modulates a carrier source, and the resultant vision -modulated carrier wave is passed to the transmitting aerial to be radiated in all directions as a broadcast vision signal.

Transmission of Sound

The sound energy information associated with the visible scene is picked up by a microphone and converted into an electronic signal which is also passed by line to the transmitting station to modulate a separate carrier source. The resultant sound -modulated carrier wave is then passed to the transmitting aerial to be radiated into the atmosphere along with the vision-modulated carrier wave.

Reception of T.V. Signals

Within a certain distance from the t.v transmitting aerial, according to the amount of radio-frequency power radiated, a t.v receiving aerial can pick up the combined vision and sound modulated wave to pass it to a t.v receiver. The receiver amplifies the received signal, and then separates the vision and sound components after a demodulation process.

The Demodulation Process

The demodulated vision signal is passed to a cathode ray tube to reproduce as closely as possible the original visible moving scene at the transmitting end. The demodulated sound signal is passed to a loud speaker to reproduce as closely as possible the original sound information associated with the visible scene. Figure 5 below shows the simple principles of a television broadcast system.

Figure 5: Simple Principles of a Television Broadcast System