Nonbroadcast Television

television facilities for transmitting and receiving visual information used for scientific, management, production, and other applications in various fields.

By the early 1970’s, several independent fields of application had emerged. Space research uses a variety of television equipment to monitor the state of astronauts’ health on board spacecraft, to visually study a planet’s surface, and to control self propelled devices. Television is used in atomic research to help handle radioactive substances at safe distances. Industrial production control uses television to provide a means of checking dimensions and configurations of parts being fabricated and of detecting defects, all without the need for direct contact and without delaying or stopping production. Television is used by controllers supervising production to maintain operational control, as in monitoring the operation of assembly lines and in marshalling cars at railroad stations.

In education, television is used to show close-ups of visual lecture material to a large audience and to televise various experiments and complicated surgical operations in color on a large screen. Underwater television, used in underwater work and research, facilitates study of the seas, emergency and rescue operations, petroleum exploration, inspection of hydraulic-engineering structures, and fishing. Television is also used in biology, physics, and astronomy and in the military. Automated processing of televised information in various control systems is made possible by computers.

Nonbroadcast television uses the same physical principles as broadcast television. Closed-circuit television systems are usually used, and in most cases, the circuitry, parameters, and structural design are dictated by the particular operating conditions and the characteristics of the objects being observed. Television equipment used in space research, for example, must have minimum weight and excellent reliability, must function without adjustment for long periods of time, and must require a minimum of power. Unlike television broadcasting, general-purpose nonbroadcast television uses transmitting equipment comprising one or several (up to 12) television transmitting cameras; the equipment is simple and is therefore usually designed to be operated by remote control. All the camera operations, such as focusing, turning, and tilting, are performed by an operator who, along with the receiving apparatus with its display monitor, is located some distance from the camera. The television transmitting tubes used are vidicons and image orthicons.

Series-produced nonbroadcast television equipment is usually similar to standard broadcast equipment, with parameters that match those specified by the television standard in broadcast television. This is done in order to utilize standardized assemblies, circuitry, and devices, as well as conventional, mass-produced television receivers. Differences may exist in the number of scanning lines in the image. If the frequency spectrum of the television signal is to be narrowed, the number of lines is reduced; if improved resolution is required, the number is increased. Other differences may exist in aspect ratio; for example, in a video telephone it is advisable to make the height of the image greater than its width. Interlaced scanning may not be employed for the sake of simplicity.