Cable-saving type CCTV system

Abstract: A cable-saving type CCTV system for transmitting a multiplexed video signal over a single coaxial cable (15) connecting a camera site (11, 12) and a control site (13, 14) by frequency-modulating a bi-directional audio signal (124, 134) and producing a digital control signal and a digital alarm signal and multiplexing the resultant signals and an external synchronizing signal in a blanking period of the video signal (122, 123, 125, 126, 132, 135, 136).

Description: BACKGROUND OF THE INVENTION This invention relates to a system for controlling camera-site equipment from a plurality of control sites in the field of monitoring and surveillance, and more particularly to a centralized control system of equipment at the control sites from a master controller at a control site. Figs. 3 and 4 are block diagrams of a system for controlling camera-site peripheral equipment in a conventional closed circuit television system (hereafter referred to CCTV). Fig. 3 shows a direct control method, while Fig. 4 shows an indirect control method. In Figs. 3 and 4, reference numeral 31 denotes peripheral equipment at the camera site, 32 denotes a controller for controlling the camera-site equipment, 33 denotes a coaxial cable, 34 denotes a multi-conductor cable, and 35 denotes a receiver for receiving signals from the controller 32 and sending signals to the camera-site equipment. The control system of Fig. 3 is of the direct control method, and sends signals and electric power in accordance with the control function of the controller 32 directly to the camera-site peripheral equipment through the multi-conductor cable 34. The control system of Fig. 4, which is of the indirect control system and used where the controller 32 and the camera-site peripheral equipment are remote from each other, performs ON/OFF control of relay contacts (not shown) of the receiver 35 through the multi-conductor cable 34, and sends necessary signals and electric power through the multi-conductor cable 34 to the camera-site peripheral equipment 31 under control in accordance with ON/OFF actions of the relay contacts of the receiver 35. Video signals from the camera are transmitted through the coaxial cable 33 to the controller 32. In the above-mentioned systems, a multi-conductor cable is required for control of the peripheral equipment, and in addition, when bi-directional voice information and unidirectional alarm information from the camera site are required, separate cables need to be provided for the speech communication and alarm transmission circuits. Fig. 5 is a block diagram of the conventional CCTV including speech communication and alarm transmission circuits. In Fig. 5, reference numerals 31 to 35 denote the same parts as shown in Figs. 3 and 4. In Fig. 5, however, alarm information from the camera site is inputted into the receiver 35, and through the intermediary of the receiver 35, the alarm information is transmitted to the controller 32 by means of the multi-conductor cable 34. Reference numerals 36, 39 denote microphones, 37, 40 denote amplifiers for increasing the strength of voice input signals, and 38, 41 denote speakers. In this way, the voice signals are transmitted in two directions. However, in the conventional systems, a video signal, bi-directional voice signal, control signal, alarm signal, and external synchronizing signal are transmitted through separate individual circuits. Therefore, in installing a control system, many cables have to be laid between the devices, making the installation work complicated and causing us to incur a large total installation cost. In addition, when there are a video signal processing unit and a camera-site control unit in mixed form of a control system in the control site, those units cannot be operated centrally, so that control operation of them is difficult. SUMMARY OF THE INVENTION This invention has been made to solve the above problem, and has as its object to provide a CCTV system of cable-saving type. GB-A-2 022 963 discloses a communication system including an apparatus 1 connected to a controller (not shown) and a TV monitor set 4 connected by a single cable. Apparatus 1 accepts a video signal from a camera 2 and an audio signal from a microphone 3, and the video signal is added to the frequency modulated audio signal and transmitted to the controller through the single cable. The controller transmits a control signal to the apparatus. Since the apparatus has insulating capacitors or filters, the control signal which is a DC signal or which is at a frequency other than UHF, is fed along the cable without interfering with the video signal. What is known from US-A-4,714,959 is a closed circuit television system including a console and a camera which are connected by a single cable to each other. The control signal from the console is transmitted during the vertical back porch period of the video signal. According to the invention, the above object is achieved by a CCTV system comprising: (a) a single cable for transmitting signals; (b) camera-site equipment, connected to said cable, comprising: a video camera for providing a video signal onto said cable, (c) at least one control-site means, operatively associated with said camera-site equipment through said cable, comprising: input means for inputting a control signal for controlling said camera-site equipment, first audio signal control means for providing a first audio signal which is frequency modulated and for demodulating a second audio signal, and first multiplex means for multiplexing said control signal and said frequency modulated first audio signal to form a first composite signal and outputting said first composite signal onto said cable; (d) signal processing means, operatively associated with said camera-site equipment and said control-site means through said cable, comprising: second audio signal control means for providing said second audio signal to be transmitted to said control-site means and for demodulating said first audio signal received from said control-site means, and second multiplex means for adding said frequency modulated second audio signal to said video signal to form a second composite signal and outputting said second composite signal onto said cable, characterized by (b) said camera-site equipment further comprising an external sync signal separation circuit for receiving an external sync signal, (c) said control-site means further comprising means for generating and outputting said external sync signal which is used to synchronize a plurality of cameras connected to the control-site means, said plurality of cameras including said video camera, wherein said first multiplexing means further adds said external sync signal to said first composite signal so as to be included therein, said external sync signal and said control signal are placed in a blanking period of a vertical sync signal of said video signal, and said external sync signal is extracted from said first composite signal by said sync signal separation circuit in said camera-site equipment which receives said first composite signal, (d) said signal processing means further comprising alarm interface means for accepting an alarm signal which is to be transmitted to said control-site means, wherein said second multiplexing means further adds said alarm signal to said second composite signal so that said alarm signal is superposed on said video signal in a blanking period of a vertical sync signal thereof. Preferably, the input means comprises a key-board. Furthermore, it is preferred that the first and second audio signal control means comprise respectively FM modems having carrier frequencies higher than a frequency band of the video signal. Furthermore, the first multiplex means in the controlsite means may transmit the first composite signal during the blanking period of the vertical synchronizing signal of the video signal. According to another preferred embodiment the control signal includes a shakehand signal. Preferably, furthermore, the cable is a coaxial cable. Finally, it is preferred that the video camera and the camera-site equipment are provided for monitoring and surveillance; and that a plurality of control-site means are operatively associated with the camera-site equipment through the cable. According to this invention, the camera site and the control site can be connected by a single coaxial cable, so that redundant cables between the units can be eliminated and saved, which makes the installation work and control operation easy. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A and 1B show the composition of the cable-saving CCTV system according to an embodiment of this invention; Figs. 2A, 2B, and 2C are timing charts of various signals transmitted multiplexed in time division over a coaxial cable in the case of NTSC signals according to the embodiment of this invention; Figs. 3 and 4 are block diagrams of conventional CCTV systems; and Fig. 5 is a block diagram of a conventional CCTV system including voice and alarm transmission circuits. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1A and 1B show the composition of the cable-saving type CCTV system according to an embodiment of this invention. Fig. 1A shows a system configuration, while Fig. 1B shows its block diagram. In those figures, camera-site peripheral equipment 11 comprises a camera function control block 111, a CPU 112, an external synchronizing signal separating circuit 113, and a communication control block 114. A receiver 12 comprises a pantilt unit housing function control block 121, an 1/F circuit 122 for receiving an alarm signal, a CPU 123, an FM modem 124 with a microphone input and an audio output, a communication control block 125, and an adder 126. Reference numerals 13, 14 denote controllers, each comprising an external synchronizing signal superposing circuit 131, a key input control block 132, a CPU 133, an FM modem 134 with a microphone input and an audio input, a communication control block 135, and an adder 136. The operation of the above embodiment will be described. In the above embodiment, at the camera site, a bi-directional audio signal is inputted through the microphone input into the receiver 12, while at the control site, a bi-directional audio signal is likewise inputted through the microphone input into the controllers 13, 14. The inputted audio signal is frequency-modulated by the FM modems 124, 134 and multiplexed with a video signal (generated by the camera and transmitted over the coaxial cable). The multiplexed signal is passed through the communication control blocks 125, 135 and transmitted over the coaxial cable 15. The multiplexed signal is then demodulated to an audio signal by the FM modem 124, 134 in the receiver 12 and the controller 13 or 14. On the other hand, an alarm signal is inputted through the I/F circuit 122 of the receiver 12 and control signals are inputted through the key input control blocks 132 of the controllers 13, 14, and those signals are sent to the CPU 123 and the CPU 133, where those signals are superposed as pulse signals in each vertical blanking period of the video signal. The CPU performs the following functions: (1) controls inputs of an alarm signal, a key operation signal, etc.; (2) exchanges signals with the electronic circuit (gate array) in the communication control block 135, multiplexes resultant signals in a specified area (blanking period), and takes out to demodulate (decode) and outputs such multiplexed signals. In other words, CPU 123 and CPU 133 each controls the formation of serial signals by multiplexing, while CPU 112 controls the formation of parallel signals for control of various pieces of the camera-site equipment from the serial signals; (3) performs communication control to enable the operations of (1) and (2) in synchronized manner as a system over the single coaxial cable connected between the devices. Figs. 2A, 2B, and 2C show examples of superposition of various signals transmitted over a coaxial cable when NTSC (National Television System Committee) signals are used. Fig. 2A shows the control signal, alarm signal, shakehand signal, and external synchronizing signal, which are multiplexed in an odd field of the video signal. The BLK denotes a blanking signal portion. Synchronized with the 11th through 14th SYNC pulses during a blanking period, control signals, each formed of four 8-bit pulse signals, are transmitted from the controller to the receiver or the camera-site equipment. Likewise, an alarm signal is received by a sensor such as an infrared detector (not shown) and supplied into the receiver, where the alarm signal is multiplexed to the video signal. The multiplexed signal is transmitted to the controller and used to operate the camera with respect to the object under surveillance. Synchronized with the 15th through 18th SYNC pulses in a blanking period, a shakehand signal, composed of four 8-bit pulse signals, for confirming that the receiver or the camera-site equipment received a control signal correctly is transmitted to the controller. At the falling edge of the third SYNC pulse (i.e., edge of the 3rd horizontal line portion) in the blanking period, an external synchronizing signal is multiplexed to the video signal. Fig. 2B is a timing chart of the above-mentioned various signals multiplexed in an even field period of the video signal. Fig. 2C shows the bi-directional audio multiplexing method, and indicates the relation between the video signal band, and FM carriers (1), (2) for transmission of bi-directional audio signals by microphone input into the receiver 12 or the controller 13. An alarm signal transmitted from the receiver 12 is decoded by the controllers 13, 14 and converted into a H(high)/L(Low) signal, while control signals transmitted from the controllers 13, 14 are converted from serial into parallel signals by the receiver 12 or the camera-site peripheral equipment. An external synchronizing signal is generated, multiplexed and transmitted by the external-synchronizing-signal superposing circuits 131 of the controllers 13, 14. And, the transmitted external-synchronizing-signal is separated synchronously by the external synchronizing signal separating circuit 113 in the camera-site peripheral equipment 11 so as to synchronize a plurality of cameras connected to the controllers 13, 14. Various forms of controls can be effected on the devices in the control sites, such as image processing devices including a multi-picture unit and a frame switcher (not shown) by use of control signals superposed and transmitted over a single coaxial cable.

Claims: A CCTV system comprising: (a) a single cable (15) for transmitting signals; (b) camera-site equipment (11), connected to said cable, comprising: a video camera for providing a video signal onto said cable, (c) at least one control-site means (13), operatively associated with said camera-site equipment through said cable, comprising: input means (132) for inputting a control signal for controlling said camera-site equipment, first audio signal control means (134) for providing a first audio signal which is frequency modulated and for demodulating a second audio signal, and first multiplex means for multiplexing said control signal and said frequency modulated first audio signal to form a first composite signal and outputting said first composite signal onto said cable; (d) signal processing means (12), operatively associated with said camera-site equipment and said control-site means (13) through said cable, comprising: second audio signal control means (124) for providing said second audio signal to be transmitted to said controlsite means (13) and for demodulating said first audio signal received from said control-site means (13), and second multiplex means for adding said frequency modulated second audio signal to said video signal to form a second composite signal and outputting said second composite signal onto said cable, characterized by (b) said camera-site equipment (11) further comprising an external sync signal separation circuit (113) for receiving an external sync signal, (c) said control-site means (13) further comprising means (131) for generating and outputting said external sync signal which is used to synchronize a plurality of cameras connected to the control-site means, said plurality of cameras including said video camera, wherein said first multiplexing means further adds said external sync signal to said first composite signal so as to be included therein, said external sync signal and said control signal are placed in a blanking period of a vertical sync signal of said video signal, and said external sync signal is extracted from said first composite signal by said sync signal separation circuit (113) in said camera-site equipment (11) which receives said first composite signal, (d) said signal processing means (12) further comprising alarm interface means (122) for accepting an alarm signal which is to be transmitted to said control-site means (13), wherein said second multiplexing means further adds said alarm signal to said second composite signal so that said alarm signal is superposed on said video signal in a blanking period of a vertical sync signal thereof. The CCTV system according to claim 1, wherein said input means (132) comprises a keyboard. The CCTV system according to claim 1 or 2, wherein said first and second audio signal control means (124, 134) comprise respectively FM modems having carrier frequencies higher than a frequency band of said video signal. The CCTV system according to any preceding claim, wherein said first multiplex means in said control-site means (13) transmits said first composite signal during the blanking period of the vertical synchronizing signal of said video signal. A system according to any preceding claim, wherein said control signal includes a shakehand signal. The CCTV system according to any preceding claim, wherein said cable (15) is a coaxial cable. The CCTV system according to any preceding claim, wherein said video camera and said camera-site equipment (11) are provided for monitoring and surveillance; and a plurality of control-site means (13; 14) are operatively associated with said camera-site equipment (11) through said cable (15). The CCTV system according to any proceding claim, wherein said second composite signal is a color video composite signal.

Inventors: KIMURA TAKAYUKI, MATSUMOTO HAJIME, OTA KAZUO, SOMA SATOSHI, KIMURA, TAKAYUKI, MATSUMOTO, HAJIME, OTA, KAZUO, SOMA, SATOSHI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1990
Main classification: H04N5
IPC codes: H04N7