JP2011061331A - Monitoring camera system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monitoring camera system reducing quality degradation caused by noise in a high frequency video signal to be transmitted, while protecting a monitoring camera and a video receiver from an induced voltage by thunder. <P>SOLUTION: As for the configuration of the monitoring camera system, a monitoring camera 111 and a video receiver 112 are connected with a coaxial cable 113, and an arrester 114 is also connected to the coaxial cable 113. The arrester 114 has: a protection circuit for protecting the monitoring camera 111 and the video receiver 112 from a surge voltage guided to the coaxial cable 113. The arrester 114 also has: an arrester metal case for accommodating the protection circuit; a ground terminal for grounding the protection circuit to the ground; an external conductor connection terminal for connecting the protection circuit to an outer conductor of the coaxial cable; a center conductor connection terminal for connecting a center conductor of the coaxial cable to the protection circuit; and a switching means for switching the connection of the arrester metal case. The switching means switches the connection of the arrester metal case according to the state of noise to a video signal received with the video receiver. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surveillance camera system, and more particularly to a surveillance camera system in which a surveillance camera and a video receiving device that receives video signals from the surveillance camera are connected by a coaxial cable.

  In recent years, with the improvement of performance of surveillance cameras and industrial cameras, video systems that transmit high-frequency video signals from cameras to video receivers using coaxial cables are often used. The coaxial cable is composed of a central conductor and an outer conductor disposed so as to surround the central conductor, and a high-frequency video signal is propagated as a transmission path having the central conductor and the outer conductor as a reciprocating conductor. The outer conductor also has an electromagnetic shielding function.

  At this time, if the wiring of the coaxial cable is in a place that is susceptible to electromagnetic influences such as outdoors, an induced voltage of lightning may be induced in the coaxial cable. There is a risk that overvoltage and overcurrent due to lightning induction may invade and destroy surveillance cameras and video receivers.

  Therefore, it is effective to use a coaxial cable arrester in order to effectively protect against lightning. A lightning arrester for a coaxial cable is connected in series to the coaxial cable, and is configured to flow an induced voltage of lightning induced in the central conductor and the outer conductor of the coaxial cable to the ground through a ground line (see, for example, Patent Document 1). ).

  This type of lightning arrester for a coaxial cable is usually connected to the center conductor and the outer conductor of the coaxial cable, has a terminal for grounding, and has a structure in which the lightning arrester circuit is entirely covered with a metal casing. The metal housing also has an electromagnetic shield function for the lightning arrester circuit, but depending on the noise environment at the installation location, the presence or absence of connection between the metal housing of the lightning arrester for the coaxial cable and the outer conductor of the coaxial cable can be a noise reduction effect. It is known to have a big impact.

  The situation of electromagnetic noise contamination in the surveillance camera system will be described in further detail.

  In the surveillance camera system, high-frequency video signals are transmitted between the surveillance camera and the video receiver via a coaxial cable. In such a surveillance camera system, the high-frequency video signal propagates between the center conductor and the outer conductor of the coaxial cable.

  Since the outer conductor of the coaxial cable is used as a return current path for the high-frequency signal current flowing through the central conductor, the outer conductor of the coaxial cable is connected to a reference point (0V line) or a point called ground of the electronic circuit. As a result, when the external conductor is connected to the metal housing of the surveillance camera and the video receiving device, and when these metal housings are grounded to the ground, both are at the same potential as the reference point, and the transmitted high-frequency video signal is external noise. It is the composition which is not influenced by.

  At this time, external noises such as broadcast waves and radio waves are prevented by setting the surveillance camera and the metal housing of the video receiver to the same potential as the reference point of the surveillance camera system. A surge arrester is inserted into the coaxial cable to protect the surveillance camera system against overvoltage that induces a relatively large potential. In this lightning arrester insertion location, the coaxial cable outer conductor is connected to the ground via a lightning arrester.

  By connecting a lightning arrester between the outer conductor of the coaxial cable and the earth, the outer conductor connection part of the lightning arrester is connected to the earth through the lightning arrester, so normally it has a high resistance value of 50 MΩ or more. Although it is insulated from the ground, when a relatively large induced voltage is generated by induced lightning or the like, it is in a conductive state and an induced current is passed through the ground.

  Also, in an environment where there is a noise current that leaks to the ground from other electrical equipment, etc., connecting an electronic circuit reference point to the ground may make it more susceptible to noise due to wraparound from the connection position to the ground. There is.

  In addition, when a lightning arrester for a surveillance camera is connected to a surveillance camera system, the outer conductor of the coaxial cable that is covered with a metal object such as a braided wire is physically cut off, but the external conductor connection of the lightning arrester It is in a state of being electrically connected to the part. Some lightning arresters have the outer conductor of the coaxial cable electrically insulated from the lightning arrester metal housing, and such a lightning arrester may not be able to obtain a shielding effect.

  In some cases, the external conductor connection portion of the lightning arrester for the surveillance camera and the metal casing are electrically connected. In this case, it is assumed that a lightning arrester is installed in a metal rack cabinet, and the rack cabinet is often connected to the ground to prevent electric shock. It may be affected by noise.

JP 2000-50494 A

  From the various situations described above, a configuration is desired in which the connection between the outer conductor of the coaxial cable, the ground, and the lightning arrester metal casing can be freely selected according to the environmental conditions such as the noise generation state and the lightning protection state of the surveillance camera system. Yes.

  The present invention has been made in view of the above points, and provides a surveillance camera system capable of reducing quality deterioration due to noise of a transmitted high-frequency video signal while protecting the surveillance camera and the video receiver from lightning induced voltage. The purpose is to do.

The present invention is a surveillance camera system in which a surveillance camera and a video receiving device that receives a video signal from the surveillance camera are connected by a coaxial cable,
It is connected to the coaxial cable, and it is configured to connect a lightning arrester including a protection circuit that protects the surveillance camera and the video receiving device from surge voltage induced in the coaxial cable.
The lightning arrester
A lightning arrester metal casing made of a conductive material and containing a protection circuit;
A grounding terminal that is insulated from the lightning arrester metal housing and grounds the protection circuit to the ground,
An outer conductor connection terminal that is insulated from the lightning arrester metal housing and connects the protection circuit to the outer conductor of the coaxial cable, and a center conductor connection terminal that connects the central conductor of the coaxial cable to the protection circuit
Switching means for switching the connection of the lightning arrester metal housing to a state in which it is connected to the ground terminal, a state in which it is connected to the external conductor connection terminal, and a state in which either the ground terminal or the external conductor connection terminal is disconnected. The connection of the lightning arrester metal casing can be switched according to the environmental conditions such as the noise state of the signal received by the device and the lightning protection state.

The switching means is
A first screw hole connected to a ground pattern connected to the ground terminal of the protection circuit and insulated from the lightning arrester metal housing;
Connected to the external conductor connection pattern connected to the external conductor connection terminal of the protection circuit, the second screw hole portion insulated from the lightning arrester metal housing, and the lightning arrester metal housing corresponding to the first screw hole portion. A first hole provided, and
The lightning arrester metal housing has a second hole provided corresponding to the second screw hole,
By connecting a lightning arrester metal housing to the ground terminal by screwing a screw into the first screw hole through the first hole portion of the lightning arrester metal housing,
The lightning arrester metal housing is connected to the external conductor connection terminal by screwing a screw into the second screw hole portion through the second hole portion of the lightning arrester metal housing.

  Further, the switching means includes a switch device that connects the lightning arrester metal housing to the ground terminal when the operation knob is in the first position, and connects the lightning arrester metal housing to the external conductor connection terminal when the operation knob is in the second position. It is configured.

Further, the switching means is
A first insert connected to a ground pattern connected to a ground terminal of the protection circuit and insulated from the lightning arrester metal housing;
A second insertion part connected to the outer conductor connection pattern connected to the outer conductor connection terminal of the protection circuit and insulated from the lightning arrester metal housing;
A first hole provided in the lightning arrester metal housing corresponding to the first insertion portion;
The lightning arrester metal housing has a second hole provided corresponding to the second insertion portion,
A pin is screwed into the first insertion portion through the first hole of the lightning arrester metal housing to connect the lightning arrester metal housing to the ground terminal, and the second through the second hole of the lightning arrester metal housing. The lightning arrester metal casing is connected to the external conductor connection terminal by screwing a pin into the insertion portion.

  The present invention relates to a surveillance camera system in which a surveillance camera and a video receiving device that receives a video signal from the surveillance camera are connected by a coaxial cable, wherein a connection of a lightning arrester metal housing is connected to a ground terminal, an external conductor connection terminal Switching means for switching to a state in which both the ground terminal and the external conductor connection terminal are disconnected, and a lightning arrester metal casing according to the noise state and lightning protection state of the video signal received by the video receiving device By switching the connection, it is possible to switch the connection between the lightning arrester metal housing and the outer conductor of the coaxial cable according to the noise status, lightning protection status, etc. and the installation status of each device. Since the effect of reducing electromagnetic wave noise can be easily switched, quality deterioration due to noise of high-frequency video signals in surveillance camera systems is reduced. Kill.

It is a system configuration figure of one example of the present invention. It is a block block diagram of the lightning arrester 114. FIG. It is a disassembled perspective view of the lightning arrester 114. FIG. It is a perspective view of the apparatus main body of the lightning arrester 114. FIG. It is a back surface side top view of the lightning arrester 114. FIG. It is a block diagram of the modification of the lightning arrester. It is a disassembled perspective view of the modification of the lightning arrester. It is a back surface side top view of the modification of the lightning arrester.

  FIG. 1 shows a system configuration diagram of an embodiment of the present invention.

  The surveillance camera system 100 of the present invention connects a surveillance camera 111 and a video receiving device 112 that receives video signals from the surveillance camera 111 via coaxial cables 113a, 113b, and 113c.

  The monitoring camera 111 is composed of, for example, a camera using a CCD, and captures an image around the monitoring target. The monitoring camera 111 converts the captured video into a high frequency video signal and outputs it from one end of the coaxial cable 113a. The other end of the coaxial cable 113b is connected to the lightning arrester 114. The high-frequency video signal output from the monitoring camera 111 is supplied to the lightning arrester 114 through the coaxial cable 113a.

  The lightning arrester 114 is also called a protector or the like, and is provided in the vicinity of the monitoring camera 111. The lightning arrester 114 is connected to one end of the coaxial cable 113b and a ground cable 119 having one end grounded to the ground. The lightning arrester 114 transmits the high-frequency video signal supplied through the coaxial cable 113a to the coaxial cable 113b through the protection circuit. The protection circuit allows a surge voltage induced in the coaxial cable 113b to flow to the ground through the grounding cable 119. One end of the grounding cable 119 is connected to the protection circuit, and the other end is grounded.

  FIG. 2 shows a block diagram of the lightning arrester 114.

  The lightning arrester 114 includes voltage protection circuits 121, 122, 123, switching means 125, a lightning arrester metal casing 126, coaxial connectors 127, 128, and a ground terminal T31.

  The coaxial connector 127 is formed of, for example, a BNC connector, and a BNC connector attached to one end of the coaxial cable 131b is attached. The coaxial connector 127 includes a center conductor connection terminal T11 and an external conductor connection terminal T12. The center conductor connection terminal T11 is connected to the center conductor of the coaxial cable 131b on the coaxial connector 127 side, and is connected to the center conductor connection terminal T21 of the coaxial connector 128 on the inner side of the lightning arrester 114.

  Similarly to the coaxial connector 127, the coaxial connector 128 is formed of, for example, a BNC connector, and a BNC connector attached to one end of the coaxial cable 131a is attached. The coaxial connector 128 includes a center conductor connection terminal T21 and an external conductor connection terminal T22. The center conductor connection terminal T21 is connected to the center conductor of the coaxial cable 131a on the coaxial connector 127 side, and is connected to the center conductor connection terminal T11 of the coaxial connector 127 on the inner side of the lightning arrester 114.

  The outer conductor connection terminal T12 of the coaxial connector 128 is connected to the outer conductor of the coaxial cable 131b on the coaxial connector 127 side, and is connected to the outer conductor connection terminal T22 of the coaxial connector 128 on the inner side of the lightning arrester 114.

  The voltage protection circuit 121 is disposed inside the lightning arrester metal casing 126 and is connected between the center conductor connection terminals T11 and T21 of the coaxial connectors 127 and 128 and the ground terminal T31. The voltage protection circuit 122 is disposed inside the lightning arrester metal casing 126 and is connected between the external conductor connection terminals T12 and T22 of the coaxial connectors 127 and 128 and the ground terminal T31. The voltage protection circuit 123 is disposed inside the lightning arrester metal casing 126 and is connected between the center conductor connection terminals T11 and T21 of the coaxial connectors 127 and 128 and the outer conductor connection terminals T12 and T22 of the coaxial connectors 127 and 128. Is done.

  The voltage protection circuits 121, 122, and 123 are circuits that prevent the voltage between the two electrodes from rising above a set voltage. For example, voltage protection elements such as a lightning arrester, a Zener diode, and a thyristor are used. It is configured to include.

  The ground terminal T31 is grounded via the ground cable 119.

  The lightning arrester 114 protects devices such as the monitoring camera 111 connected to the coaxial cables 113a, 11b and the like by the voltage protection circuits 121, 122, 123.

  The switching means 125 includes ground connection screw holes A, B, C, and a ground switching screw 131. The ground connection screw hole A is connected to the outer conductor connection terminal T12 of the coaxial connector 127, the outer conductor connection terminal T22 of the coaxial connector 128, and one end of the voltage protection circuit 122. The ground connection screw hole B is connected to the other ends of the voltage protection circuits 121 and 122 and the ground terminal T31. The ground connection screw hole C is in an insulated state and is not connected anywhere. Further, the ground connection screw holes A, B, and C are insulated from the lightning arrester metal casing 126.

  3 is an exploded perspective view of the lightning arrester 114, FIG. 4 is a perspective view of the main body of the lightning arrester 114, and FIG.

  The lightning arrester metal casing 126 is composed of a conductive material plate such as stainless steel, and is composed of an upper metal casing 126a and a lower metal casing 126b. Inside the lightning arrester metal casing 126, the apparatus main body 141 is attached in a state so as to be electrically insulated from the lightning arrester metal casing 126.

  The apparatus main body 141 is composed of printed wiring boards 142 and 143. On the printed wiring boards 142 and 143, any of coaxial connectors 127 and 128, a ground terminal T31, and voltage protection circuits 121, 122, and 123 are mounted. The printed wiring board 142 and the printed wiring board 142 are connected by connection pins 144 or the like.

  The printed wiring board 142 and the printed wiring board 143 are arranged in parallel to each other, and components constituting the coaxial connectors 127 and 128, the ground terminal T31, and the voltage protection circuits 121, 122, and 123 are arranged therebetween. With the above configuration, the apparatus main body 141 is reduced in size.

  The apparatus main body 141 is electrically fixed to the lower lightning arrester metal casing 126b by a screw 147 through a spacer 145 made of an insulator.

  The upper metal casing 126a is fixed to the lower metal casing 126b with screws 148. The upper metal casing 126a and the lower metal casing 126b are electrically fixed to each other.

  At this time, the coaxial connectors 127 and 128 and the ground terminal T31 are electrically insulated from the lightning arrester metal casing 126 by screws 149, washers 150, and the like.

  In the lower metal casing 126b, through holes 151a, 151b, and 151c are formed at positions corresponding to the ground connection screw holes A, B, and C. The ground switching screw 131 is screwed into the ground connection screw hole AC through the through holes 151a, 151b, and 151c.

  When the ground switching screw 131 is screwed into the ground connection screw hole A from the outside of the lightning arrester metal housing 126, the lightning arrester metal housing 126 and the ground connection screw hole A are electrically connected to each other. When the screw is inserted into the ground connection screw B from the outside, the lightning arrester metal casing 126 and the ground connection screw hole B are electrically connected, and the lightning arrester metal casing 126 is screwed into the ground connection screw hole C from the outside. Then, the arrester metal casing 126 and the ground connection screw hole C are electrically connected.

  The lightning arrester metal casing 126 is connected to the outer conductors of the coaxial cables 113a and 113b via the outer conductor connection terminals T12 and T22 of the coaxial connectors 127 and 128 by screwing the ground switching screw 131 into the ground connection screw hole A. be able to. Further, by screwing the ground switching screw 131 into the ground connection screw B, the lightning arrester metal casing 126 can be grounded via the ground terminal T31 and the grounding cable 119. Furthermore, the lightning arrester metal casing 126 can be electrically insulated by screwing the ground switching screw 131 into the ground connection screw hole C.

  Even when the lightning arrester metal casing 126 is electrically insulated by screwing the ground switching screw 131 into the ground connection screw hole C, the ground switching screw 131 is fixed to the lightning arrester metal casing 126. Therefore, loss of the ground switching screw 131 can be prevented.

  The lightning arrester 115 has the same configuration as the lightning arrester 114, and is connected to the other end of the coaxial cable 113b. The lightning arrester 115 is provided in the vicinity of the video receiving device 112. One end of the coaxial cable 113 c and one end of the grounding cable 120 are connected to the lightning arrester 115. The other end of the grounding cable 120 is grounded. The lightning arrester 115 allows the surge voltage induced in the coaxial cables 113b and 113c to flow to the ground through the grounding cable 120.

  The other end of the coaxial cable 113 c is connected to the video receiving device 112. The video receiving device 112 includes, for example, a video server, a video recorder, and the like. The video receiving device 112 is connected to the monitor 118. The video receiving device 112 receives a high-frequency video signal from the monitoring camera 111 and causes the monitor 118 to display or record.

  According to the present embodiment, the switching means 125 of the lightning arresters 114 and 115 connects the lightning arrester metal casing 126 to the external conductor connection terminals T11 and T21 according to the state of the high-frequency image received by the video receiving device 112. Alternatively, the high-frequency video signal can be obtained by switching the lightning arrester metal housing 126 to the ground terminal T31 or switching the lightning arrester metal housing 126 to the external conductor connection terminals T11, T21 and the ground terminal T31. The influence of noise on the can be reduced.

  For example, in the monitoring camera system 100 shown in FIG. 1, the lightning arresters 114 and 115 are installed at positions as close as possible to the monitoring camera 111 and the video reception device 112, respectively. At this time, normally, the lightning arrester metal casing 126 is grounded, and it is possible to prevent the arrester metal casing 126 from being charged due to various electrical influences and becoming electrically unstable. At this time, as noise that may affect the quality of the video signal, noise current that leaks to the ground from nearby electrical equipment or the like wraps around from the ground, and electromagnetic wave noise in the space causes printed circuit board of the lightning arrester 114 A case is assumed in which the outer conductor and the center conductor are guided and enter.

  When the noise current leaking to the ground from the former electrical equipment or the like goes around from the ground and enters, it is possible to prevent the intrusion of noise by removing the lightning arrester metal casing 126 from the ground and cutting the path. When electromagnetic noise in the latter space is guided and invaded by the external conductor and the central conductor on the printed circuit board of the lightning arrester 114, the lightning arrester metal casing 126 is connected to the external conductor terminals T12 and T22 through the switching means 125. By switching to, the lightning arrester metal casing 126 serves as a shield that continues from the outer conductor of the coaxial cables 113a, 113b, 113c, and the outer conductor and the center conductor on the printed circuit board of the lightning arrester 114 can be shielded from electromagnetic noise.

  The lightning arresters 114 and 115 have, for example, a high lightning protection function (8/20 μs, 20 kA). Moreover, it is set as the structure which has a high-speed lightning surge responsiveness of nanosecond order. In addition, transmission from DC to 30 MHz is possible, that is, high-definition television signal transmission is possible.

  According to the present embodiment, in the monitoring camera system 100 in which the monitoring camera 111 and the video receiving device 112 that receives the video signal from the monitoring camera 111 are connected by the coaxial cables 113a, 113b, and 113c, the lightning arrester metal of the lightning arresters 114 and 115 is used. There is provided switching means 125 for switching the connection of the casing 126 to a state where it is connected to the ground terminal, a state where it is connected to the external conductor connection terminal, and a state where both the ground terminal and the external conductor connection terminal are disconnected. The connection state of the lightning arrester metal casing 126 can be switched according to the state of noise and the lightning protection state of the high-frequency video signal to be transmitted, so that the monitoring camera 111, the video receiver 112, and the coaxial cables 113a, 113b, 113c The lightning arresters 114 and 11 according to the installation conditions of the devices such as the lightning arresters 114 and 115 Arrester metal housing 126 and the coaxial cable 113a, 113b, it is possible to switch whether a connection to 113c of the outer conductor, thereby, possible to easily reduce the quality degradation due to noise of the high-frequency video signal.

  In place of the ground switching screw 131, a ground switching pin may be used, and the ground connection screw holes A, B, and C may be configured by three insertion holes for inserting the ground switching pin. By using a pin, the connection of the lightning arrester metal casing 126 can be switched by attaching / detaching the pin to / from the insertion hole, so that a rotating operation such as screwing is not required like a screw. It is possible to improve the work efficiency of the switching operation of 126 connections.

  In the lightning arresters 114 and 115 of this embodiment, the connection of the lightning arrester metal casing 126 by the switching means 125 is switched by replacing the ground switching screw 131 and the pin. Good.

  6 is a block diagram of a modified example of the lightning arrester 114, FIG. 7 is an exploded perspective view of the modified example of the lightning arrester 114, and FIG. In the figure, the same components as those in FIGS. 2, 3 and 5 are denoted by the same reference numerals, and the description thereof is omitted.

  In the lightning arrester 214 of this modification, the switching means 225 is composed of a switch 231. The switch 231 is mounted on the lower surface side of the printed wiring board 142 and is electrically connected to the printed wiring board 142 and the lightning arrester metal casing 126. The switch 231 is configured such that the operation knob 231a is exposed outward from the opening 232 of the lower metal casing 126b.

  The operation knob 231a of the switch 231 can take three positions Pa, Pb, and Pc. In the switch 231, when the operation knob 231a is at the position Pa, the lightning arrester metal casing 126 is connected to the node ta. The node ta is connected to the external conductor connection terminals T12 and T22 of the coaxial connectors 127 and 128. Therefore, by positioning the operation knob 231a at the position Pa, the lightning arrester metal casing 126 is connected to an external conductor such as the coaxial cables 113a, 113b, 113c through the external conductor connection terminals T12, T22 of the coaxial connectors 127, 128. The

  In the switch 231, when the operation knob 231a is at the position Pb, the lightning arrester metal casing 126 is connected to the node tb. The node tb is connected to the ground terminal T31. For this reason, by placing the operation knob 231a at the position Pb, the lightning arrester metal casing 126 is grounded to the ground through the ground terminal T31.

  The switch 231 has the lightning arrester metal casing 126 connected to the node tc when the operation knob 231a is at the position Pc. The node tc is in an open state and is not connected anywhere. For this reason, by positioning the operation knob 231a at the position Pc, the lightning arrester metal casing 126 is opened and is not connected anywhere.

  According to this modification, the connection of the lightning arrester metal casing 126 can be easily switched by operating the operation knob 213a.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be considered without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 100 Surveillance camera system 111 Surveillance camera, 112 Image | video receiving apparatus 113a, 113b, 113c Coaxial cable 114, 115, 214 Lightning arrester 121, 122, 123 Voltage protection circuit 124 Zener diode pair, 125, 225 Switching means 126 Lightning arrester metal housing, 126a Upper metal casing, 126b Lower metal casing 127, 128 Coaxial connector 131 Ground connection screw 142 Printed wiring board 231 Switch, 231a Operation knobs A, B, C Ground connection screw holes T11, T21 Central conductor connection terminals, T12, T22 External conductor connection terminal T31 Ground terminal

Claims (4)

A monitoring camera system that connects a monitoring camera and a video receiving device that receives a video signal from the monitoring camera with a coaxial cable,
It is connected to the coaxial cable, and is configured to connect a lightning arrester including a protection circuit that protects the monitoring camera and the video receiving device from a surge voltage induced in the coaxial cable,
The lightning arrester is
A lightning arrester metal housing made of a conductive material and containing the protection circuit;
A grounding terminal that is insulated from the lightning arrester metal housing and grounds the protection circuit to the ground;
An outer conductor connection terminal that is insulated from the lightning arrester metal housing and connects the protection circuit to an outer conductor of the coaxial cable;
A central conductor connection terminal for connecting a central conductor of the coaxial cable to the protection circuit;
Switching means for switching the connection of the lightning arrester metal housing to a state connected to the ground terminal, a state connected to the external conductor connection terminal, a state where both the ground terminal and the external conductor connection terminal are disconnected,
The switching camera is a surveillance camera system in which the connection of the lightning arrester metal casing can be switched in accordance with the state of noise to the video signal received by the video receiving device. The switching means is connected to a ground pattern connected to the ground terminal of the protection circuit, and a first screw hole portion insulated from the lightning arrester metal housing,
A second screw hole connected to the outer conductor connection pattern connected to the outer conductor connection terminal of the protection circuit and insulated from the lightning arrester metal housing;
A first hole provided in the lightning arrester metal housing corresponding to the first screw hole; and
The lightning arrester metal housing has a second hole provided corresponding to the second screw hole,
By screwing a screw into the first screw hole through the first hole of the lightning arrester metal housing, the lightning arrester metal housing is connected to the ground terminal,
The surveillance camera according to claim 1, wherein the lightning arrester metal casing is connected to the external conductor connection terminal by screwing a screw into the second screw hole through the second hole of the lightning arrester metal casing. system. The switching means connects the lightning arrester metal housing to the ground terminal when the operation knob is in the first position, and connects the lightning arrester metal housing to the external conductor connection terminal when the operation knob is in the second position. The surveillance camera system according to claim 1, wherein the surveillance camera system is configured by a switch device. The switching means is connected to a ground pattern connected to the ground terminal of the protection circuit, and a first insertion portion insulated from the lightning arrester metal housing,
A second insertion portion connected to an outer conductor connection pattern connected to the outer conductor connection terminal of the protection circuit and insulated from the lightning arrester metal housing;
A first hole provided in the lightning arrester metal housing corresponding to the first insertion portion;
The lightning arrester metal housing has a second hole provided corresponding to the second insertion portion,
By connecting a pin to the grounding terminal by inserting a pin into the first insertion portion through the first hole of the lightning arrester metal housing,
The surveillance camera system according to claim 1, wherein the lightning arrester metal casing is connected to the external conductor connection terminal by inserting a pin into the second insertion portion through the second hole of the lightning arrester metal casing.

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