JPH04207491A - Changeover device for video camera - Google Patents

Abstract

PURPOSE:To switch only input terminals connecting to a video camera cyclically sequentially with simple constitution by giving a control signal representing an input terminal of the camera to be selected in response to the count of a presettable counter to a switching means. CONSTITUTION:Video cameras 1-6 are connected to prescribed six input terminals 1A-6A through coaxial cables 1B-6B and input their output to a central control section 7. The central control section 7 is provided with a camera changeover section 8, a DC power supply 9, a comparator 10, a presettable counter 11, a daisy switch 12 setting a preset value to the counter 11, and a decoder 13 decoding a count output of the counter 11 and the input terminals 1A-6A of the cameras 1<-6> are selected in response to the count of the counter 11 to update cyclically the count for each input of a selection signal. Thus, video output signals from the video cameras 1-6 are selected efficiently.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a video camera switching device that selects and extracts a video output signal from one of a plurality of video cameras. [Prior art 1] Conventionally, for example, on the monitor side, a selection signal for switching the video camera is generated each time a switch is pressed, and each time the selection signal is received, the switching device selects each signal from each video camera. Select the line input terminals one by one. [Problem to be Solved by the Invention 1] The switching device has a predetermined number of input terminals, and each time a selection signal is input, each of all the input terminals is sequentially and cyclically selected. Therefore, if signal lines from each video camera are not connected to all input terminals, input terminals to which no video cameras are connected will also be selected, and the greater the number, the worse the efficiency will be. Therefore, an object of the present invention is to provide a switching device for a video camera that solves the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for selecting a video camera from a video camera connected to a corresponding input terminal among a plurality of input terminals based on a control signal indicating the input terminal of the camera to be selected. a switching means for selecting and outputting a video signal; a counter that can be preset and updates the count value cyclically each time a selection signal is input; a setting means for setting a preset value of the counter; and a counter for the counter. It is characterized by comprising a control means for applying a control signal to the switching means indicating the input terminal of the camera to be selected in response to the value. [Function j] According to the present invention, with the above configuration, only the input terminals to which the video cameras are connected can be sequentially selected, and the video output signals from each video camera can be efficiently selected. [Example 1] Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an entire embodiment of the present invention. In this figure, 1 to 6 are video cameras, and predetermined 6
It is connected to the input terminals IA to 6A at the locations by coaxial cables 18 to 6B. 7 is a central control unit that manually controls the video output of each camera 1 to 6, and selects and outputs the video signal from the corresponding input terminal based on a control signal indicating the input terminal to be selected from the decoder described later. It has a camera switching section 8, a DC power supply 9, a comparator 10, a presettable counter 11, a digital switch 12 for setting a preset value of the counter 11, and a decoder 13 for decoding the count value output of the counter 11. ing. 14 is a coaxial cable for transmitting the selected video camera output, and 15 to 17 are monitor devices connected in parallel. However, the third monitor device 17 is provided with a termination resistor RT to achieve impedance matching with the coaxial cable. Next, the operation of the embodiment shown in FIG. 1 will be explained. Assuming that the digital switch 12 is set to "3", the preset value of the counter 11 is "3", and the counter 11 receives the preset value every time the output pulse from the comparator 10 is input to the count input. Cyclically count down (or up) the value up to. The decoder inputs the count output signal from the counter 11, and inputs a control signal indicating the input terminal corresponding to the count value to the camera switching unit 8. This camera switching section 8
Based on the control signal from the decoder 13, the video cameras connected to the corresponding input terminals are sequentially selected. For example, when the count value of the counter 11 is "3", the third video camera 3 connected to the input terminal 3A is selected in the camera switching unit 8, and the video signal from the camera 3 is transmitted via the coupling capacitor C. The signal is output to the coaxial cable 14 and supplied to the monitor side. On the other hand, due to the action of the DC power supply 9, a constant DC voltage ■ is applied to the core wire of the coaxial cable 14 via the resistor R. , continues to be applied. In other words, a certain DC offset component is superimposed on the video signal being output to the coaxial cable 14. Each of the monitor devices 15 to 17 is provided with switches SWI to SW3 for grounding the core wire, so when any of these switches is closed, the grounding side is connected to the DC power supply 9 via the resistor R. A current flows through the coaxial cable 14.
The core wire drops to a potential slightly higher than ground potential. Therefore, each time the switch is closed, the voltage drop is detected by the comparator 10 and input as a selection signal to the count input of the counter 11. Counts down every time a selection signal is input. for example,
In the above example, when the selection signal is generated once, the counter 1
The count value of 1 becomes "2", and the decoder 13 inputs a control signal to the camera switching unit 8 based on this count value, and the camera switching unit 8 is connected to the input terminal 2A based on the input control signal. select the second video camera 2. Similarly, when the next selection signal is generated, the count value of the counter 11 becomes "1", and the camera switching section 8 selects the first video camera 1. When the next selection signal is generated, the counter 11 carries out, the count value becomes "3", and the third video camera 3 is selected again. In this way, only the number of input terminals set by the digital switch 12 are cyclically and sequentially selected by the camera switching unit 8, so that, for example, input terminals IA and 2A. A video camera is connected to each terminal 3A, and input terminal 4
If a video camera is not connected to A, 5A, or 6A, by setting the digital switch 12 to "3", only the input terminal to which the video camera is connected will be cyclically sequentially selected every time the selection signal is generated. You can choose. In order to prevent the video signal from leaking to the power supply side, the DC power supply 9 described above preferably generates a DC voltage through the emitter and collector of a transistor, as shown in FIG. That is, the alternating current impedance between the emitter and collector is made sufficiently high so that only the direct current component is superimposed on the coaxial cable 14. Note that the diode between the base and collector is an element for compensating temperature characteristics. A capacitor for a DC element is connected in series to a terminating resistor RTM, and with this configuration, it is possible to prevent a minute current from flowing from the DC power supply 9 to the ground side. Although the configuration is such that it is included in the central control unit 7, this DC power supply is used to DC-offset the video signal, so it may be provided anywhere.For example, it may be provided within a certain monitor device. In addition, in Fig. 1, the switch S built in each monitor device is
The core wire of the coaxial cable is grounded by Wl to SW3, as shown in FIG. 4. It is also possible to connect to ground via the variable voltage source VBA. By doing so, it is possible to lower (or increase) the voltage of the core wire of the coaxial cable to an arbitrary voltage, so it is also possible to generate a plurality of types of camera switching signals. However, in that case, multiple comparators are required. Furthermore, in place of the switches SWI to SW4, a pulse signal generation circuit, a modulated signal generation circuit, etc. are connected,
It is also possible to generate multiple types of camera switching signals. [Effects of the Invention J As described above, according to the present invention, only the input terminals to which video cameras are connected can be sequentially switched cyclically with an extremely simple configuration, which is extremely efficient.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the entire embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a DC power supply, FIG. 3 is a diagram showing another example of the termination method, and FIG. 4 is another example. FIG. 1-6... Video camera, 7... Central control unit, 8... Camera switching unit, 9... DC power supply, lO... Comparator, 11... Counter, 12... Digiswitch , 13...decoder. 14...Coaxial cable, 15-I7...Monitor device, C...Capacitor, RTM...Terminal resistor, R1...Resistor.

Claims (1)

[Claims] 1) Switching that selects and outputs a video signal from a video camera connected to a corresponding input terminal among a plurality of input terminals based on a control signal indicating the input terminal of the camera to be selected. means, a counter that can be preset and cyclically updates a count value each time a selection signal is input; setting means for setting a preset value of the counter; and a camera to be selected in response to the count value of the counter. A switching device for a video camera, comprising: control means for applying a control signal indicating an input terminal to the switching means.