This invention relates to improvements in the cable transmission of video signals over long distances from spaced locations remote from a central location at which the signals can be received and monitored.
It is often desirable to use a number of video cameras at locations remote from a central location to record activities at such remote locations. For instance, a conventional baseband (non-RF) system uses a number of remote cameras directly connected by individual coaxial lines to the inputs of a matrix switching apparatus at a central location whose output is connected to a video monitor. Such a system operates effectively if the distance from each camera to the matrix switching apparatus is less than several thousand feet. Since each camera has its own coaxial cable connecting the camera to the matrix switching apparatus at the central location, this results in high cable costs and excessive cable bundle size over such a distance.
In another multi-camera system of conventional design, a CATV system allows video signals to be distributed over considerably greater distances such as a number of miles between a central location and the various camera locations. However, each camera at a remote location has a RF video modulator interfacing the camera to a broadband coaxial or fiber-optic cable. The CATV system requires a demodulator at a central location for each modulator, respectively, the output of each demodulator being switched by a matrix switching apparatus to one or more video monitors.
The requirement for separate RF modulators and companion demodulator for each camera gives rise to large equipment costs as well as requiring a considerable amount of space for the demodulators at the central location. However, the use of broadband techniques and hardware allows a bundle of individual cables, such as is required for the baseband system described above, to be replaced with one broadband cable or fiber-optic cable. Also, this technology allows for two-way control suitable for camera position control and supervision.
Because of the relatively high costs and space requirements of conventional broadband systems of the type described, a need exists for improvements in broadband video systems which minimize such costs and space requirements without sacrificing the quality of video signals received at a central location from video cameras at remote locations. The present invention satisfies this need.