CN112954135B - Unidirectional isolation transmission control device for audio and video signals - Google Patents
Unidirectional isolation transmission control device for audio and video signals Download PDFInfo
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- CN112954135B CN112954135B CN202110210750.1A CN202110210750A CN112954135B CN 112954135 B CN112954135 B CN 112954135B CN 202110210750 A CN202110210750 A CN 202110210750A CN 112954135 B CN112954135 B CN 112954135B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/04—Synchronising
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L63/00—Network architectures or network communication protocols for network security
- H04L63/02—Network architectures or network communication protocols for network security for separating internal from external traffic, e.g. firewalls
- H04L63/0227—Filtering policies
- H04L63/0236—Filtering by address, protocol, port number or service, e.g. IP-address or URL
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/222—Studio circuitry; Studio devices; Studio equipment
- H04N5/262—Studio circuits, e.g. for mixing, switching-over, change of character of image, other special effects ; Cameras specially adapted for the electronic generation of special effects
- H04N5/268—Signal distribution or switching
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/015—High-definition television systems
Abstract
The invention provides an audio and video signal unidirectional isolation transmission control device which comprises a case, a power supply, an HDMI video signal unidirectional transmission isolation switching device, an audio unidirectional transmission isolation switching device and a signal synchronous switching control circuit. The invention realizes that the internal and external network audio and video signals share the basic function of the same display large screen and audio system in a one-key switching mode, and output control and switching design are carried out on HDMI audio and video signals and related power supplies, so that the dual-network HDMI audio and video signals are not contacted with each other.
Description
Technical Field
The invention relates to the field of audio and video network security, in particular to a unidirectional isolation transmission control device for audio and video signals.
Background
HDMI is a high-definition multimedia standard, is a digital video/audio signal interface technology, is a special digital interface suitable for video transmission, can simultaneously transmit audio and video signals, and has a maximum data transmission speed of 48Gbps. The HDMI interface has simple structure and strong anti-interference capability, and has become a main standard interface of multimedia video display equipment such as a television, a display, an LED screen and the like. At present, most multimedia video display equipment is internally provided with a loudspeaker, and can directly output audio signals transmitted by an HDMI interface synchronously with videos. However, in some specific use environments, such as a secure conference, the audio and video outputs must be provided by two different devices and controlled independently.
In some command and scheduling scenes, due to the confidentiality requirement of the intranet audio and video information, according to relevant regulations, the intranet audio and video information is required to ensure that signal isolation is realized with the audio and video information of an external network, so that the audio and video signals are prevented from passing. However, when an emergency occurs, not only the video information of the intranet needs to be displayed, but also the audio and video information from other networks needs to be displayed through a large screen, so that the situation of the event can be comprehensively mastered in real time, and the efficiency and the accuracy of handling the emergency by related personnel of a command center are improved.
How to switch and display the internal and external network video information through a large screen, realizing the non-contact of the dual-network audio and video signals in a large screen system, realizing the signal isolation of the dual-network audio and video information at the same time, meeting the requirement of safety and confidentiality and being the problem to be solved.
Disclosure of Invention
In view of the above, the present invention aims to realize signal isolation of the intranet and extranet audio/video signals, avoid audio/video signal leakage, further prevent physical unpacking damage, and meet requirements of confidentiality and security while sharing and displaying the large screen and the audio system in a one-key switching manner.
In order to achieve the above object, the present invention provides an audio/video signal unidirectional isolation transmission control device, which comprises a chassis, an HDMI video signal unidirectional transmission isolation switching device, an audio unidirectional transmission isolation switching device, and a signal synchronous switching control circuit:
the HDMI video signal one-way transmission isolation switching device comprises a first signal processing circuit, a second signal processing circuit, a third signal processing circuit, a video signal switching control circuit and a video one-way circuit, wherein the first signal processing circuit, the second signal processing circuit and the third signal processing circuit are used for reshaping, filtering and synchronous processing of HDMI signals, interference of noise waves is removed, the HDMI video signals of a first network are reshaped, filtered and synchronously processed by the first signal processing circuit and then sent to the video signal switching control circuit, the HDMI video signals of a second network are reshaped, filtered and synchronously processed by the second signal processing circuit and then sent to the video signal switching control circuit, the video signal switching control circuit selects one of the HDMI video signals of the two networks to be output under the control of the signal synchronous switching control circuit, the output HDMI video signals are reshaped, filtered and synchronously processed by the third signal processing circuit and then sent to a screen for display through the video one-way circuit, and the video one-way circuit prevents reverse leakage of signals of a display large screen;
the audio unidirectional transmission isolation switching device comprises a first power supply switching control circuit, a second power supply switching control circuit, a first audio unidirectional circuit, a second audio unidirectional circuit, an audio signal switching control circuit and a signal processing circuit, wherein a first network audio signal is sent into the first audio unidirectional circuit, a second network audio signal is sent into the second audio unidirectional circuit, the output ends of the first audio unidirectional circuit and the second audio unidirectional circuit are connected with the audio signal switching control circuit, the first network power supply is controlled by the first power supply switching control circuit to supply power to the first audio unidirectional circuit, the second network power supply is controlled by the second power supply switching control circuit to supply power to the second audio unidirectional circuit, the first power supply switching control circuit and the second power supply switching control circuit are controlled by the signal synchronous switching control circuit, only one connected power supply is powered on at the same time, the audio signal switching control circuit is controlled by the signal synchronous switching control circuit, the network audio signal sent by the audio unidirectional circuit to the signal processing circuit, the first network audio signal and the second network signal are selected to be sent to the signal processing circuit, and the audio signal processing circuit is sent to a zero-noise-floating processing device for eliminating the audio signal playing;
the signal synchronous switching control circuit is connected with the video signal switching control circuit, the first power supply switching control circuit, the second power supply switching control circuit and the audio signal switching control circuit, and controls the connection of the four switching control circuits to be switched from a first network to a second network synchronously or from the second network to the first network synchronously after receiving a switching instruction.
Furthermore, the video unidirectional circuit adopts an MAX3814 chip, 4 pairs of differential signals of the HDMI video signals are input from an input interface of the chip, after level judgment is carried out by an equalizer in the chip, the HDMI video signals are output from a corresponding output interface, 200 omega resistors are bridged at the output ends of each pair of differential signals, common mode offset of the output ends is reduced to the minimum, signal echoes are reduced, and a reverse output channel does not exist; the first audio unidirectional circuit and the second audio unidirectional circuit both adopt an LM386 audio integrated power amplifier chip, audio signals are connected to an input pin of the chip, an amplifier in the LM386 audio integrated power amplifier chip amplifies the audio signals and then outputs the amplified audio signals, and a reverse output channel does not exist.
Furthermore, the video signal switching control circuit, the first power supply switching control circuit, the second power supply switching control circuit and the audio signal switching control circuit are switched by adopting a relay switch.
Furthermore, the signal synchronous switching control circuit adopts a driver chip to realize the synchronous switching of the relay switch.
Further, the driver chip is LN2003, and the signal synchronous switching control circuit adopts a mode in which the driver chip implements synchronous switching of the relay switch, which is a mode in which a plurality of driver chips LN2003 are connected in parallel: the input ends of the driver chip LN2003 are connected together to receive a switching instruction, and the output ends of the driver chip LN2003 are respectively connected with the control ends of one relay switch; and the second is to adopt a two-stage cascade mode of the driver chips LN2003, the driver chips LN2003 of the first stage are connected in parallel, the input ends of the driver chips LN2003 of the second stage are connected together and receive a switching instruction, the input ends of each driver chip LN2003 of the second stage are connected together and connected with one of the output ends of the driver chip LN2003 of the first stage, and the output ends of the driver chip LN2003 of the second stage are respectively connected with the control end of one relay switch.
Furthermore, the case is a tamper alarm case, which comprises a case shell, a microswitch with a driving rod and a tamper circuit, when the case shell is closed, the driving rod of the microswitch is pressed to open the microswitch, when the case is detached, the driving rod of the microswitch springs open, the microswitch is closed, the tamper circuit is triggered to alarm and the power supply of the audio/video signal one-way isolation transmission control device is disconnected.
Furthermore, the case shell is a hexahedron and comprises a front cover plate and an upper cover plate, the rest four sides are integrally bent and welded, the case can be disassembled to open the front cover plate or open the upper cover plate, when the front cover plate and the upper cover plate are installed, a microswitch with a driving rod is firstly placed, the driving rod is in a pressing state, and the microswitch is in an opening state; when the front cover plate or the upper cover plate is opened, the corresponding driving rod is caused to bounce, the micro switch is closed, the anti-disassembly circuit is triggered to alarm, and the power supply of the audio/video signal unidirectional isolation transmission control device is disconnected.
Furthermore, the anti-dismantling circuit comprises an alarm circuit and a power supply control circuit, the power supply control circuit controls the power supply of the audio/video signal unidirectional isolation transmission control device, the power supply control circuit comprises an input end, a control end and a control end, an external power supply is connected with the input end of the power supply control circuit, and the control end controls the output end to be connected with the external power supply or disconnected with the external power supply;
the alarm circuit comprises a battery, a fuse, a diode, a triode, a microswitch, an alarm, a first resistor, a second resistor, the positive pole of the battery is connected with the positive pole of the diode, the negative pole of the diode is connected with the input end of an external power supply, the emitting pole of the triode and one end of the fuse are connected with the two ends of the first resistor respectively, the source pole of the triode and the emitting pole are connected with the source pole of the triode, the other end of the fuse and one end of the microswitch are connected with the other end of the second resistor, the control end of the power supply control circuit is connected, the other end of the microswitch is connected to the negative pole of the battery, the positive pole of the alarm is connected after the collector pole of the triode and the source pole are connected, and the negative pole of the battery is connected with the negative pole of the alarm.
Furthermore, when the microswitch is closed, the anode and the cathode of the battery are communicated with two ends of the fuse, so that the current in the fuse is increased instantly, the fuse is blown, and the audio and video signal unidirectional isolation transmission device has no power input, thereby ensuring that the equipment cannot supply power and cannot work normally; the positive and negative electrodes of the battery are respectively communicated with the base electrode and the emitter electrode of the triode, the base electrode and the emitter electrode are in a saturated state, the collector electrode and the emitter electrode are conducted, and at the moment, the alarm is communicated with the positive and negative electrodes of the battery, so that the alarm gives an alarm.
Further, the power supply control circuit is a relay switch.
Advantageous effects
The audio and video signal one-way isolation transmission control device provided by the invention realizes that the internal network and external network audio and video signals share the basic functions of the same display large screen and audio system in a one-key switching mode, and output control and switching design are carried out on the HDMI audio and video signals and related power supplies, so that the double-network HDMI audio and video signals in the large screen system are not contacted with each other, the signal isolation and confidentiality requirements of the double-network audio and video information are met, the reverse signal leakage generated by the signals is avoided, and the requirements of internal and external network confidential places are met.
The invention is based on the control of the electromagnetic relay switch, realizes that the audio and video signals of two mutually isolated networks share the same spliced display large screen and audio system by matching with the control circuit, the filter circuit, the unidirectional output circuit and the anti-dismounting protection device, synchronously switches and outputs the audio and video signals, ensures the signal isolation between all input signals and the isolation and synchronous switching of two network power supplies in the signal switching process, and is suitable for the use of internal and external network security scenes.
Drawings
Fig. 1 is an external connection schematic diagram of the audio/video signal unidirectional isolation transmission control device of the invention.
Fig. 2 is a functional principle schematic diagram of the audio/video signal unidirectional isolation transmission control device of the invention.
Fig. 3 is a schematic diagram of a video signal unidirectional isolation transmission circuit according to the present invention.
Fig. 4 is a schematic circuit diagram of a driver chip LN2003 used for synchronous switching in the present invention.
FIG. 5 is a schematic diagram of a synchronous switching control circuit according to the present invention.
Fig. 6 is a perspective view of the chassis of the audio/video signal unidirectional isolation transmission control device of the invention.
Fig. 7 is a perspective view of the open state of the cabinet of the audio/video signal unidirectional isolation transmission control device of the invention.
Fig. 8 is a schematic diagram of an anti-disassembly circuit of the audio/video signal unidirectional isolation transmission control device.
Fig. 9 is a schematic diagram of a power supply control circuit of the audio/video signal unidirectional isolation transmission control device of the invention.
Fig. 10 is a schematic diagram of an alarm circuit of the audio/video signal unidirectional isolation transmission control device.
Detailed Description
The following describes in detail embodiments of the present invention with reference to the drawings.
The large screen of the command center controls the displayed image content through a large screen splicing control system, but a large screen splicing controller cannot realize signal isolation of input audio and video signals, so that in the traditional command center, the large screen can only display audio and video information of the same network. And if the user wants to display the audio and video information of another network, the audio and video information is displayed on a large screen in other places. The invention aims to solve the problems, simultaneously realizes the switching display of audio and video information of different networks on a large screen in one place, and keeps the signal isolation state between signals during the audio and video display and switching, thereby meeting the requirement of confidentiality regulation.
As shown in fig. 1, the audio/video signal unidirectional isolation transmission control device of the present invention is connected to a large display screen, an audio system, an audio/video source and power supply of a first network, and an audio/video source and power supply of a second network, so as to realize unidirectional transmission of audio/video signals of the first network or the second network, and realize that audio/video signals of different networks are played on the same large display screen and the audio/video system while ensuring signal isolation of the audio/video signals of the first network and the second network.
The video information of two networks which are mutually isolated is switched and displayed through the large screen, so that the efficiency and the accuracy of related personnel for handling emergency events can be improved. And the audio and video information of the internal network is required to be isolated from the audio and video information of the external network according to requirements. Therefore, the isolation switching equipment provided by the invention can meet the signal isolation and confidentiality requirements of the audio and video information of the internal and external networks, can realize non-contact of the audio and video signals of the internal and external networks in a large-screen system, and supports large-screen one-key switching of the video image pictures of the internal network and the external network.
As shown in fig. 2, the audio/video signal unidirectional isolation transmission control device of the present invention includes a chassis, a power supply, an HDMI video signal unidirectional transmission isolation switching device, an audio unidirectional transmission isolation switching device, and a signal synchronous switching control circuit:
the HDMI video signal one-way transmission isolation switching device comprises a first signal processing circuit, a second signal processing circuit, a third signal processing circuit, a video signal switching control circuit and a video one-way circuit, wherein the first signal processing circuit, the second signal processing circuit and the third signal processing circuit are used for shaping, filtering and synchronizing HDMI signals, interference of foreign waves is removed, the HDMI video signals of a first network are shaped, filtered and synchronized through the first signal processing circuit and then sent to the video signal switching control circuit, the HDMI video signals of a second network are shaped, filtered and synchronized through the second signal processing circuit and then sent to the video signal switching control circuit, the video signal switching control circuit selects one of the HDMI video signals of the two networks to output under the control of the signal synchronizing switching control circuit, the output HDMI video signals are shaped, filtered and synchronized through the third signal processing circuit and then sent to a screen for display, and the video one-way circuit prevents reverse leakage of signals of a display large screen.
The audio unidirectional transmission isolation switching device comprises a first power supply switching control circuit, a second power supply switching control circuit, a first audio unidirectional circuit, a second audio unidirectional circuit, an audio signal switching control circuit and a signal processing circuit, wherein a first network audio signal is sent into the first audio unidirectional circuit, a second network audio signal is sent into the second audio unidirectional circuit, the output ends of the first audio unidirectional circuit and the second audio unidirectional circuit are connected with the audio signal switching control circuit, the first network power supply is controlled by the first power supply switching control circuit to supply power to the first audio unidirectional circuit, the second network power supply is controlled by the second power supply switching control circuit to supply power to the second audio unidirectional circuit, the first power supply switching control circuit and the second power supply switching control circuit are controlled by the signal synchronous switching control circuit, only one connected power supply is powered on at the same time, the audio signal switching control circuit is controlled by the signal synchronous switching control circuit, the network audio signal sent by the audio unidirectional circuit connected with the power supply to the signal processing circuit, and the audio signal processing circuit is selected to play a zero-noise-floating signal and play device;
the signal synchronous switching control circuit is connected with the video signal switching control circuit, the first power supply switching control circuit, the second power supply switching control circuit and the audio signal switching control circuit, and controls the connection of the four switching control circuits to be switched from a first network to a second network synchronously or from the second network to the first network synchronously after receiving a switching instruction. The switching command is generated by the keys on the control switching key box shown in fig. 1 and transmitted through a network cable, or transmitted through an electric signal generated by other methods.
The video signal switching control circuit, the first power supply switching control circuit, the second power supply switching control circuit and the audio signal switching control circuit are switched by adopting a relay switch. The invention adopts the electromagnetic isolation function of the signal relay switch to respectively carry out electromagnetic isolation and switching on the video signal and the audio signal, thereby realizing the signal isolation and switching of the video signal of a display large screen and the audio signal in the audio playing equipment.
In the specific embodiment of the invention, the MAX3814 chip of MAXIM corporation is adopted to realize the unidirectional transmission guarantee of the HDMI video signal, that is, the MAX3814 chip is adopted as the video unidirectional circuit. MAX3814 is a TMDS equalization/driver chip to compensate for the loss of FR-4 circuit board and cable to HDMI connector. The chip is generally used for the HDMI cable and is used for prolonging the transmission distance of the HDMI signals, so that the jitter allowance of a cable channel at the receiving end of the connector is improved. The audio/video signal unidirectional isolation transmission control device inputs HDMI video signals (namely 4 pairs of differential signals) through the chip, as shown in figure 3, the HDMI video signals are input from input interfaces INA +/INA-, INB +/INB-, INC +/INC-, IND +/IND-and are output from corresponding OUTA +/OUTA-, OUTB +/OUTB-, OUTC-, OUTD +/OUTD-through-after-outputs after level judgment is carried out by using an equalizer in the chip, 200 omega resistors are connected to differential output ends, common mode offset of the output ends is reduced to the minimum, signal echoes are reduced, and a path for backward output does not exist, so that the video signals cannot be transmitted reversely, namely the video signals cannot be transmitted from a display screen to a front-end input device, and the video signals of an internal network are prevented from being leaked by the isolation effect of an electromagnetic relay and the suppression backward transmission effect of a video unidirectional circuit. In addition, the MAX3814 chip is used for solving the problems of unidirectional signal transmission and signal isolation switching of the HDMI signals, meanwhile, the transmission distance of the HDMI signals is increased, and the driving capability of output signals is improved. The transmission distance of the HDMI signals which are not output by the device is 10-15 meters, and the transmission distance of the HDMI signals which are output by the device is 60-80 meters.
In order to ensure the one-way transmission function of the audio signal, firstly, signal amplification circuits are respectively arranged on two isolation network audio circuits to be used as an audio one-way circuit and an electromagnetic relay to carry out isolation switching, so that the audio signal is prevented from leaking through an audio signal channel; and secondly, the two paths of audio channels are respectively provided with independent power supplies and are switched and controlled, so that audio signals are prevented from leaking through a power supply circuit.
In the specific embodiment of the invention, an LM386 audio integrated power amplifier chip of UTC company is adopted to ensure the unidirectional transmission of audio signals, namely, an LM386 is adopted as an audio unidirectional circuit. The audio input signal is accessed to the input pin of the chip and then enters the amplifier for signal transmission, and a reverse output channel does not exist, so that the signal is ensured not to be transmitted from the internal network audio equipment to the external network audio equipment. Meanwhile, for the audio circuit part, the power supplies of the two isolation networks adopt two completely independent power supply inputs, so that the isolation of the power supply part is ensured. Furthermore, the audio and video signal unidirectional isolation transmission control device also thoroughly isolates the switching control part from the audio and video signal transmission part of the large-screen system by utilizing the electromagnetic isolation effect of the relay switch.
In the specific implementation mode of the invention, the relay switch adopts a two-input one-output switch, and the two input ends of the relay switch are used for thoroughly isolating signals of two networks, thereby realizing the isolation of an internal network and an external network. When the intranet state is switched to: the relay switch enables the intranet circuit to be closed, the intranet power supply source supplies power, and intranet audio and video signals are output unidirectionally; at the moment, the relay switch enables the external network circuit to be disconnected and the external network power supply to stop outputting, and no external network audio and video signals are output. When switching to the extranet state: the relay switch enables the external network circuit to be closed, the external network power supply to output, and the external network audio and video signals are output in a single direction; the relay switch enables the intranet to be disconnected and the intranet power supply to stop outputting, and no intranet audio and video signals are output.
Referring to fig. 1-3, in the present invention, a video signal, an audio signal, and a power supply need to be switched synchronously, 4 pairs of differential signals of an HDMI interface need 8 relay switches, the switching control of the power supply is controlled by 1 relay, the switching control of the audio signal (a microphone signal and a sound box signal) is controlled by 2 relays, and there are many relay switches, so that it is the key function and performance of the present invention to ensure the synchronous switching of the relay switches.
In an embodiment of the present invention, the synchronous switching of the relay switches is controlled by using an inverter circuit inside a driver chip (for example, LN 2003). As shown in fig. 4, the driver chip LN2003 is composed of 7 NPN darlington transistors, forming a 7-way inverter circuit, i.e., when the input terminal is at a high level, the output terminal is at a low level; when the input end is at low level, the output end is at high level.
The principle of the control of the relay switch by the LN2003 is shown by only one LN2003 in fig. 5. The input ends of LN2003 are connected in parallel, the output ends of LN2003 are respectively connected with the control ends of signal relay switches, one input controls multi-channel output, the input end inputs a switching instruction, and the signal relay switches are controlled by controlling the high-low switching of signals, thereby realizing the synchronous switching control of the signal relay switches. As shown IN fig. 5, all input terminals of LN2003 are connected to Control signal Control _ IN1, output terminals LS1 to LS7 are connected to Control terminals of the relay switches, respectively, and Control signal Control _ IN1 can be generated by operating a Control key. When the Control signal Control _ IN1 is high, LS 1-LS 7 synchronously output low signals, and the relay switch is IN an initial state; and when the Control signal Control _ IN1 is low, LS 1-LS 7 synchronously output high signals, and the relay switch is synchronously controlled to be closed, so that the relay switch is controlled to be synchronously switched.
In an actual circuit, according to an actual situation, one mode is a mode in which a plurality of driver chips LN2003 are connected in parallel, input ends of all driver chips LN2003 are connected together to receive a switching command, and output ends thereof are connected to control ends of a plurality of relay switches, respectively, and a second mode is a mode in which the driver chips LN2003 are cascaded to solve a problem that a power of a switching control signal cannot drive an excessive number of relay switches, in which the driver chips LN2003 of a first stage are connected in parallel, input ends thereof are connected together to receive a switching command, and input ends of each driver chip LN2003 of a second stage are connected together, as shown in fig. 5, one output end of the driver chip LN2003 of the first stage is connected, and output ends of the driver chips LN2003 of the second stage are connected to control ends of a plurality of relay switches, respectively, thereby realizing a situation of synchronous output control of control signals of a plurality of relay switches by the above-mentioned cascade combination mode.
In addition, in order to further reduce the leakage risk of the audio/video signal unidirectional isolation transmission control device and avoid the operations of manual illegal disassembly and the like, a case disassembly prevention alarm circuit and a disassembly prevention structure are specially arranged. When the casing of the case is illegally opened, the audio/video signal unidirectional isolation transmission control device immediately stops working and simultaneously gives out an alarm sound.
The invention discloses a disassembly-prevention alarm case which comprises a case shell, a microswitch 2 and a disassembly-prevention alarm circuit. Referring to fig. 6 and 7, in the embodiment of the present invention, the casing is a hexahedron, and includes an upper cover plate 3, a front cover plate 4, and the rest four sides 1, which are integrally bent and welded, and when the casing is disassembled, only the front cover plate or the upper cover plate can be opened, and when the front cover plate and the upper cover plate are installed, the micro switch 2 with the driving rod is first installed, and the driving rod is in a pressing state, and at this time, the micro switch is in an opening state; when the front cover plate or the upper cover plate is opened, the corresponding driving rod is caused to bounce, and the micro switch is closed. The five positions of fig. 6 and 7 are provided with the micro switches, and the number and the positions of the micro switches can be adjusted as long as the case can be sensed to be disassembled.
As shown in fig. 8, the microswitch is connected with the anti-dismounting circuit, the anti-dismounting circuit includes an alarm circuit and a power supply control circuit, and the power supply control circuit controls the power supply of the audio/video signal unidirectional isolation transmission control device. In the specific embodiment of the invention, the 12VIN is an external 12V power supply of the equipment. The whole power supply of the circuit needs to be output through the control of the power supply control circuit, and the power supply control circuit is realized by adopting a relay switch. As shown in fig. 9, the overall POWER supply of the audio/video signal unidirectional isolation transmission control device is determined by the input signal FUSE _ POWER of the control terminal 1 pin of the POWER supply control circuit, and when the input voltage of the pin is "high", the output terminal of the relay switch outputs a 12V POWER supply to supply POWER to the overall circuit of the audio/video signal unidirectional isolation transmission control device. When the input voltage of the pin is low, the output end of the relay switch has no output voltage, and the whole circuit of the power supply control circuit is powered off and stops working.
As shown in fig. 10, the alarm circuit includes a battery, a FUSE, a diode D1, a triode Q1 (in the figure, a PNP triode), a micro switch X1, a micro switch X2 (when two or more micro switches are provided, the micro switch X2 may represent a plurality of switches except the micro switch X1), a battery X3, an alarm U1, a first resistor R1, and a second resistor R2. The specific microswitch deployment can be the deployment in the modes of fig. 6 and 7, and can also be other modes capable of detecting the opening of the chassis shell. The positive pole of the battery is connected with the positive pole of the diode, the negative pole of the external POWER supply input end is connected with the negative pole of the diode, the emitting pole of the triode and the first end of the FUSE are connected with the two ends of the first resistor respectively, the source pole of the triode is connected with the first end of the second resistor, the second end of the second resistor is connected with the second end of the FUSE and the first end of the microswitch, the POWER control end FUSE _ POWER of the POWER supply control circuit is connected, the second end of the microswitch is connected to the negative pole of the battery, the positive pole of the alarm is connected after the collector pole of the triode is connected with the source pole, and the negative pole of the battery is connected with the negative pole of the alarm.
When the audio and video signal unidirectional isolation transmission control device is in a normal POWER supply working state, the external POWER supply 12VIN is connected to the control end FUSE _ POWER of the POWER supply control circuit through the FUSE and is at a high level, the circuit is normally powered, and the equipment is in a normal working state. When the shell of the equipment case is illegally opened, namely the upper cover or the front cover is opened, the micro switch in the case is triggered, so that the driving rod of the micro switch is bounced open, and the switches X1 and X2 are closed. At the moment, the diode D1 is conducted, the anode and the cathode of the battery are communicated with the two ends of the FUSE, so that the current in the FUSE is increased instantly, the FUSE is blown, and the FUSE _ POWER at the control end of the relay switch has no voltage input, so that the equipment cannot work normally due to the fact that POWER supply is lacked. And the positive and negative electrodes of the battery are respectively communicated with the base electrode and the emitting electrode of the Q1 triode, the Q1 enters a saturated state, the collecting electrode and the emitting electrode are conducted, and at the moment, the alarm is communicated with the positive and negative electrodes of the battery, so that the buzzer alarms, and the alarm can be stopped until the electric quantity of the battery is exhausted.
When the audio-video signal unidirectional isolation transmission control device is not input by an external power supply, if the case is illegally disassembled in the state, the microswitch is closed. At the moment, the diode D1 is also conducted, and the anode and the cathode of the battery are communicated with the two ends of the fuse, so that the current in the fuse is instantly increased, the fuse is blown, the power input of the audio and video signal unidirectional isolation transmission device is invalid, and the equipment cannot be started when the power is subsequently switched on, thereby ensuring that the equipment cannot normally work after being illegally switched on; and the positive and negative electrodes of the battery are respectively communicated with the base electrode and the emitting electrode of the Q1 triode, the Q1 enters a saturated state, the collecting electrode and the emitting electrode are conducted, and at the moment, the alarm is communicated with the positive and negative electrodes of the battery, so that the alarm gives an alarm.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalents, improvements, etc. made within the principle of the present invention are included in the scope of the present invention.
Claims (10)
1. The utility model provides an audio frequency and video signal unidirectional isolation transmission controlling means which characterized in that includes quick-witted case, HDMI video signal unidirectional transmission isolation switching device, audio frequency unidirectional transmission isolation switching device and signal synchronization switching control circuit:
the HDMI video signal one-way transmission isolation switching device comprises a first signal processing circuit, a second signal processing circuit, a third signal processing circuit, a video signal switching control circuit and a video one-way circuit, wherein the first signal processing circuit, the second signal processing circuit and the third signal processing circuit are used for shaping, filtering and synchronizing HDMI signals, interference of foreign waves is removed, the HDMI video signals of a first network are shaped, filtered and synchronized by the first signal processing circuit and then sent to the video signal switching control circuit, the HDMI video signals of a second network are shaped, filtered and synchronized by the second signal processing circuit and then sent to the video signal switching control circuit, the video signal switching control circuit selects one of the HDMI video signals of the two networks to output under the control of the signal synchronizing switching control circuit, the output HDMI video signals are shaped, filtered and synchronized by the third signal processing circuit and then sent to a screen for display through the video one-way circuit, and the video one-way circuit prevents reverse leakage of signals for displaying a large screen;
the audio unidirectional transmission isolation switching device comprises a first power supply switching control circuit, a second power supply switching control circuit, a first audio unidirectional circuit, a second audio unidirectional circuit, an audio signal switching control circuit and a signal processing circuit, wherein a first network audio signal is sent into the first audio unidirectional circuit, a second network audio signal is sent into the second audio unidirectional circuit, the output ends of the first audio unidirectional circuit and the second audio unidirectional circuit are connected with the audio signal switching control circuit, the first network power supply is controlled by the first power supply switching control circuit to supply power to the first audio unidirectional circuit, the second network power supply is controlled by the second power supply switching control circuit to supply power to the second audio unidirectional circuit, the first power supply switching control circuit and the second power supply switching control circuit are controlled by the signal synchronous switching control circuit, only one connected power supply is powered on at the same time, the audio signal switching control circuit is controlled by the signal synchronous switching control circuit, the network audio signal sent by the audio unidirectional circuit connected with the power supply to the signal processing circuit, and the audio signal processing circuit is selected to play a zero-noise-floating signal and play device;
the signal synchronous switching control circuit is connected with the video signal switching control circuit, the first power supply switching control circuit, the second power supply switching control circuit and the audio signal switching control circuit, and controls the connection of the four switching control circuits to be switched from a first network to a second network synchronously or from the second network to the first network synchronously after receiving a switching instruction.
2. The apparatus for controlling unidirectional transmission of audio/video signals according to claim 1, wherein the video unidirectional circuit employs a MAX3814 chip, 4 pairs of differential signals of HDMI video signals are input from an input interface of the chip, and output from a corresponding output interface after level judgment is performed by an equalizer in the chip, and 200 Ω resistors are connected across output terminals of each pair of differential signals, so that common mode offset of the output terminals is reduced to the minimum, signal echoes are reduced, and a path for reverse output does not exist;
the first audio unidirectional circuit and the second audio unidirectional circuit both adopt LM386 audio integrated power amplifier chips, audio signals are connected to input pins of the chips and are output after being amplified by amplifiers in the LM386 audio integrated power amplifier chips, and a reverse output channel does not exist.
3. A unidirectional transmission control device for audio and video signals as claimed in claim 1, wherein the video signal switching control circuit, the first power switching control circuit, the second power switching control circuit and the audio signal switching control circuit are switched by using relay switches.
4. A unidirectional transmission control device for audio and video signals as claimed in claim 3, wherein the signal synchronous switching control circuit uses a driver chip to realize the synchronous switching of the relay switch.
5. A unidirectional isolation transmission control device for audio and video signals according to claim 4, wherein the driver chip is LN2003, and the signal synchronous switching control circuit adopts a mode that the driver chip realizes synchronous switching of a relay switch, which is a mode that a plurality of driver chips LN2003 are connected in parallel: the input ends of the driver chip LN2003 are connected together to receive a switching instruction, and the output ends are respectively connected with the control ends of the relay switches; or a two-stage cascade mode of the driver chips LN2003 is adopted, the driver chips LN2003 of the first stage are connected in parallel, the input ends are connected together to receive a switching instruction, the input ends of each driver chip LN2003 of the second stage are connected together and connected to one of the output ends of the driver chip LN2003 of the first stage, and the output ends of the driver chips LN2003 of the second stage are respectively connected to the control end of one relay switch.
6. The unidirectional isolation transmission control device for audio and video signals according to claim 1, wherein the case is a tamper alarm case comprising a case housing, a microswitch with a drive rod and a tamper circuit, when the case housing is closed, the drive rod of the microswitch is pressed to open the microswitch, when the case is detached, the drive rod of the microswitch is flicked, the microswitch is closed, the tamper circuit is triggered to alarm and the power supply of the unidirectional isolation transmission control device for audio and video signals is switched off.
7. The apparatus for controlling unidirectional transmission of audio/video signals according to claim 6, wherein the casing is a hexahedron comprising a front cover plate and an upper cover plate, and the remaining four sides are integrally bent and welded, and when the casing is disassembled, the front cover plate or the upper cover plate can only be opened, and when the front cover plate and the upper cover plate are installed, the microswitch with a driving rod is firstly placed, and the driving rod is in a pressing state, and at the moment, the microswitch is in an opening state; when the front cover plate or the upper cover plate is opened, the corresponding driving rod is caused to bounce, the micro switch is closed, the anti-disassembly circuit is triggered to alarm, and the power supply of the audio/video signal unidirectional isolation transmission control device is disconnected.
8. The audio/video signal unidirectional isolation transmission control device according to claim 6 or 7, wherein the tamper circuit comprises an alarm circuit and a power supply control circuit, the power supply control circuit controls the power supply of the audio/video signal unidirectional isolation transmission control device, the power supply control circuit comprises an input end, a control end and an output end, the external power supply is connected with the input end of the power supply control circuit, and the control end controls the output end to be connected with or disconnected from the external power supply;
the alarm circuit includes the battery, the fuse, the diode, the triode, micro-gap switch, the alarm, first resistance, the second resistance, the diode is anodal to battery positive pole connection, the negative pole of diode is connected to the external power supply input, the projecting pole of triode and the one end of fuse, triode source electrode and projecting pole are connected respectively to first resistance both ends, the one end of second resistance is connected to the source electrode of triode, the other end of fuse and micro-gap switch's one end is connected to the other end of second resistance, and connect power supply control circuit's control end, micro-gap switch's the other end is connected to the negative pole of battery, the positive pole of alarm is connected after triode collecting electrode and the source electrode link to each other, the negative pole of battery is connected to the negative pole of alarm.
9. The device for controlling audio/video signal unidirectional isolation transmission according to claim 8, wherein when the microswitch is closed, the positive and negative electrodes of the battery are communicated with the two ends of the fuse, so that the current in the fuse is instantly increased, the fuse is blown, and the audio/video signal unidirectional isolation transmission device has no power input, thereby ensuring that the device cannot supply power and cannot normally work; the positive and negative electrodes of the battery are respectively communicated with the base electrode and the emitter electrode of the triode and enter a saturated state, the collector electrode and the emitter electrode are conducted, and at the moment, the alarm is communicated with the positive and negative electrodes of the battery, so that the alarm gives an alarm.
10. The apparatus for controlling unidirectional transmission of audio/video signals according to claim 8, wherein said power supply control circuit is a relay switch.
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