Video switcher

• US 4,037,250 A
• Filed: 08/22/1974
• Issued: 07/19/1977
• Est. Priority Date: 08/22/1974
• Status: Expired due to Term

• Current Assignee: Charles L. Melanko, Everett G. Mcgahan
• Original Assignee: Charles L. Melanko, Everett G. Mcgahan
• Inventors: McGahan, Everett G., Melanko, Charles L.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Coles, Edward L.
• Application Number:
  US05/499,623
• Time in Patent Office: 1,062 Days
• Field of Search: 178/6, 178/6.8, 178/DIG. 15, 178/DIG. 23, 178/DIG. 38, 178/DIG. 13, 340/147, 325/308, 179/2 TV, 358/85, 358/108, 358/181, 358/185
• US Class Current: 348/159
• CPC Class Codes: G08B 13/19634 Electrical details of the system, e.g. component blocks for carrying out specific functions
• CPC Class Codes: G08B 13/19645 Multiple cameras, each having view on one of a plurality of scenes, e.g. multiple cameras for multi-room surveillance or for tracking an object by view hand-over
• CPC Class Codes: G08B 13/19693 using multiple video sources viewed on a single or compound screen
• CPC Class Codes: H04H 20/10 Arrangements for replacing or switching information during the broadcast or the distribution
• CPC Class Codes: H04N 5/268 Signal distribution or switching
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

A closed circuit video surveillance system having a plurality of camera stations which may be connected by entirely random and independent selection to a plurality of monitors located at different viewing stations without degradation of video quality. Each camera feeds its video signal over its own transmission line to a central switching station at which all camera signals are collected. Each viewing station has a monitor connected by a transmission line to an electromechanical switching means located in the central switching station. A selector switch is also located at the viewing station and is connected to the electromechanical switching means for controlling its operation. The electromechanical switching means switches the viewing station monitors into connection with selected cameras. Signal degradation is prevented, even if all viewing stations selected the same camera, by the use of a high impedance video amplifier and by switching in dummy input resistances to maintain a constant impedance condition.

Claims

1. A video surveillance apparatus comprising:

a. a plurality of video cameras;

b. a plurality of video viewing stations, each station equipped with a video monitor and a remote selector switch comprising means for controlling the exhibition of video signals from any selected camera; and

c. a central Master Video Switcher in direct electronic communication with each of said cameras, said monitors, and said remote selector switches, said central Video Switcher including a plurality of electrical switching means each associated with a different one of said viewing stations, each of said electrical switching means being remotely controlled by the selector switch of an associated viewing station for connecting in selected random access any selected one of said video cameras to the monitor of its associated viewing station independently of any connection between said camera or any other camera with any other viewing station.

2. The video surveillance apparatus of claim 1, having:

means for providing a substantially constant load impedance for said video cameras.

3. An apparatus according to claim 1

wherein the central Master Video Switcher is in direct electronic communication with each of said cameras by means of a separate coaxial cable.

4. An apparatus according to claim 1

wherein the central Master Video Switcher is in direct electronic communication with each of said monitors by means of a separate coaxial cable.

5. An apparatus according to claim 1

wherein the central Master Video Switcher is in direct electronic communication with each of said cameras by means of a separate coaxial cable and is in direct electronic communication with each of said monitors by means of a separate coaxial cable and

wherein the electrical switching means of the central Master Video Switcher is remotely controlled from any of said viewing stations by multiconductor low frequency cable.

6. An apparatus according to claim 1

wherein said central Master Video Switcher includes resistance means to minimize distortion even though a plurality of said monitors are in direct electronic communication through said central Master Video Switcher with a single camera.

7. A video surveillance apparatus comprising:

a. a plurality of video cameras;

b. a plurality of video viewing stations each station equipped with a video monitor and a remote selector switch having a unique state corresponding to each video camera; and

c. a central switching station in direct electronic communication with each of said cameras, said monitors and said remote selector switches, said central switching including a plurality of electrical switching means each associated with a different one of said viewing stations, each of said electrical switching means being remotely controlled by the selector switch of its associated viewing station for connecting in random access any selected one of said video cameras to the monitor of its associated viewing station;

wherein each of said electrical switching means includes a plurality of single-pole, single-throw electrical switching devices, each of said switching devices having a pair of switching terminals and a control input terminal, one switching terminal of each switching device being connected to corresponding switching terminals of the other switching devices and to the associated monitor, the other switching terminal of each switching device being connected to a different one of said cameras, and each of said control input terminals being connected to the associated remote selector switch for actuating a different one of said switching devices in response to a selected unique state of the associated selector switch.

8. A video surveillance apparatus comprising:

a. a plurality of video cameras;

a plurality of video viewing stations each station equipped with a video monitor and a remote selector switch having a unique state corresponding to each video camera; and

c. a central switching station in direct electronic communication with said cameras, said monitors and said remote selector switches, said central switching including a plurality of electrical switching means each associated with a different one of said viewing stations, each of said electrical switching means being remotely controlled by the selector switch of its associated viewing station for connecting in random access any selected one of said video cameras to the monitor of its associated viewing station;

wherein each of said electrical switching means comprises;

a plurality of effective single-pole, double-throw switching devices, each having a wiper terminal, a pair of switching terminals alternatively connectible to said wiper terminal and having a control input terminal, wherein the wiper terminals of each of said switching devices are connected together and to the associated monitor, and wherein a corresponding switching terminal of each of said switching devices is connected through a different associated resistance to a common ground and wherein the other switching terminal of each of said switching devices is connected through a coupling impedance to a different one of said cameras whereby each of said cameras is alternatively connectible to the associated monitor and to a resistance.

9. An apparatus according to claim 8 wherein said different associated resistances and said coupling impedances are all resistors having a substantially identical impedance.

10. An apparatus according to claim 9 wherein each of said cameras is connected to said common ground through terminating resistances of substantially identical impedances and wherein the impedance of each of said different associated resistances is at least ten times the product of the number of viewing stations and the impedance of any terminating resistance.

11. An apparatus according to claim 10 wherein a video amplifier is provided in the central switching station interposed in the connection between each monitor and its associated switching means, said video amplifier having an input impedance substantially higher than the impedance of said coupling impedance and an output impedance substantial matched to the input impedance of a monitor.

12. An apparatus according to claim 11 wherein each of said effective single-pole, double-throw switching devices comprises a pair of single-pole, single-throw relays having an interconnected switch terminal and wherein each of said selector switches comprises a plurality of single-pole, double-throw push button switches connected to a source of electrical power and a conductor means for permitting alternative actuation of each of said relay pairs by a different one of said single-pole, double-throw selector switches.