89 results about "Coupling transformer" patented technology

An IPD high-selectivity band-pass filter based on a weak coupling transformer technology comprises an LC parallel resonance circuit, an LC series resonance circuit, an LC parallel resonance circuit and a fourth capacitor C4, and inductors in the LC parallel resonance circuit and inductors in the LC parallel resonance circuit have a weak transformer coupling relation; the coupling coefficient required by the weak coupling transformer provided by the invention is very small and can be realized in a mode of adjacently placing metals on the same layer, so that the structural complexity of the filter is effectively reduced; the band-pass filter is based on an IPD technology, an extra decoupling equivalent inductor is introduced through a weak transformer coupling technology, the extra decoupling equivalent inductor and a parallel capacitor which is connected between the input end and the output end of the filter in a bridging mode form a new resonance path, and a transmission zero point is introduced into an upper stop band and a lower stop band of the filter respectively to improve the selectivity of the filter. According to the invention, the selectivity of the filter can be effectively improved on the premise of not additionally introducing an inductance element and not increasing the order of the filter.

According to the radio frequency power amplifier and the radio frequency chip provided by the utility model, the input end of the input matching circuit is used for receiving a radio frequency signal, the output end of the input matching circuit is connected with the input end of the power amplifier, and the first end of the filter circuit is used for connecting an external power supply voltage; the output end of the power amplifier is connected with the second end of the filter circuit, the first end of the trap circuit and the input end of the strong coupling transformer, the second end of the trap circuit is grounded, the output end of the strong coupling transformer is used for outputting radio frequency signals, the first end of the high-order trap circuit is connected with the output end of the strong coupling transformer, and the second end of the high-order trap circuit is grounded. And the second end of the high-order trap circuit is grounded. Compared with the prior art, the radio frequency power amplifier has the advantages that the radio frequency matching area is effectively reduced, the space and the cost of the radio frequency power amplifier are saved, and meanwhile, the efficiency and the performance of the radio frequency power amplifier are effectively improved through the structural design of the strong coupling transformer.

The invention discloses a broadband impedance measurement device and a broadband impedance sweep frequency measurement method, and the device comprises a main path input switch, a disturbance control and gain calculation module, a main path output switch, and single-phase measurement units, wherein the number of the single-phase measurement units is equal to the number of electric phases of a power grid. The single-phase measurement unit comprises a broadband disturbance generator, an output filtering unit, a coupling transformer, a disturbance detection unit, a bypass switch and an output voltage and current detection unit. The disturbance control and gain calculation module is connected with the disturbance detection unit, the output voltage and current detection unit and the broadband disturbance generator. The method comprises the steps of injecting disturbance according to a sweep frequency point table; extracting disturbance response voltage according to the voltage of the secondary winding of the coupling transformer; calculating a disturbance gain according to the disturbance injection voltage and the disturbance response voltage; and comparing the disturbance gain with a preset risk gain threshold value and a preset early warning gain threshold value, and performing control according to a comparison result.

The invention relates to the technical field of electromagnetic compatibility automatic testing, in particular to a power line audio conduction sensitivity automatic testing and switching system which comprises a multi-mode testing module, a data recording module, a testing analysis module, a testing control module and a result dividing module. Three test modes of high sensitivity, conventional sensitivity and low sensitivity are set, and a programmed switch group is utilized to automatically switch the connection relation between a capacitor and a coupling transformer, so that automatic configuration of different interference intensity test environments is realized. And the system automatically determines a subsequent test direction by analyzing conduction fluctuation characteristics of the transmission subsystem, and intelligently grades the anti-interference capability of the equipment based on a final test result. The problems that manual wiring is complex, efficiency is low and errors are prone to occurring in traditional testing are solved, automation and intellectualization of the testing process are achieved, testing efficiency and accuracy are remarkably improved, and meanwhile a reliable basis is provided for applicability evaluation of equipment in different electromagnetic environments.

The invention discloses a defect coupling low-noise amplifier. The low-noise amplifier solves the problem that the performance of a low-noise amplifier in the prior art is influenced by a grid source inductance coupling coefficient. Forward coupling of an input inductor and a grid inductor and reverse coupling of the input inductor and a source inductor are achieved through a unique defect coupling transformer matching network, meanwhile, reverse coupling of a grid inductor and the source inductor is achieved, and the coupling coefficient of the grid-source inductor is reduced through coupling counteracting inductance; by combining a differential common-source transconductance amplification stage, a four-order magnetic coupling resonance unit, a differential transconductance amplification stage with a neutralizing capacitor and an output transformer matching network, the characteristics of high gain bandwidth and low noise are realized; simulation and actual tests verify that the low-noise amplifier can effectively reduce the noise coefficient and broaden the input matching range, has good compatibility and wide application prospects based on a conventional integrated circuit production process, can be applied to a phased array system, and can also form a receiver system with other circuits.

The invention belongs to the technical field of electromagnetic detection, and particularly relates to an electromagnetic detection transmitting system for urban underground space and a control method, the electromagnetic detection transmitting system comprises a direct current power supply, an inverter and a load which form a traditional electromagnetic transmitting circuit, and a composite impedance matching network is connected in series between the inverter and the load; the composite impedance matching network comprises an active matching network and a passive matching network, the active matching network comprises an H bridge circuit composed of four IGBT transistors and a coupling transformer, one output end of the inverter passes through one end of the secondary side of the coupling transformer, and the primary side of the coupling transformer is connected with the H bridge circuit; and one end of the passive matching network is connected with the other end of the secondary side of the coupling transformer, the other end of the passive matching network is connected with one end of the load, and the other end of the load is connected with the other output end of the inverter, so that the situation that the emission energy of the full-aviation emission system of the unmanned aerial vehicle is weakened due to dynamic impedance change generated in actual motion is avoided.

The invention relates to the technical field of aviation electric connectors, and discloses an isolation coupler, which adopts tin soldering to fix a shell and a shell cover so as to ensure the sealing performance and the stability of the shell and prevent the influence of external interference on signal transmission. And meanwhile, the shielding layers of the signal input lead and the signal output lead are welded with the shell, so that the anti-interference capability of signal transmission can be further improved. The circuit board assembly adopts the epoxy glass cloth board with the characteristic impedance of 77 ohms, so that the stability and the consistency of signal transmission can be ensured. Moreover, a leakage protection function is realized by adopting a single-point grounding structure of the first coupling transformer, a discharge path is provided for common-mode noise, the safety and reliability of the isolation coupler can be improved, and meanwhile, a ground loop can be cut off and power frequency interference can be eliminated by adopting a single-point grounding structure of the second coupling transformer, so that the accuracy of signal transmission is improved.

Various embodiments disclose a cross-inductor voltage regulator comprising a first switching circuit configuration pair, the first switching circuit configuration pair comprising a first set of switching circuits, a first compensating coupled inductor coupled to the first set of switching circuits, a second set of switching circuits, and a second compensating coupled inductor coupled to the second set of switching circuits, wherein the first compensating coupled inductor comprises a first winding of a compensating coupled transformer and the second compensating coupled inductor is a second winding of the compensating coupled transformer.

A distributed ice melting device topological structure suitable for an ultra-high voltage power transmission line comprises a plurality of ice melting sub-modules arranged in a distributed mode, and each ice melting sub-module comprises a single-turn coupling transformer, a metal oxide voltage limiter, a bypass switch, a filter, an H-bridge current converter and a direct-current capacitor. A primary winding of the single-turn coupling transformer is directly formed by split sub-conductors of the ultra-high voltage power transmission line, and a secondary winding of the single-turn coupling transformer is electrically connected with other parts of the ice melting sub-modules, so that the ice melting sub-modules are connected in series on the split sub-conductors of the power transmission line in a distributed manner; the H-bridge current converter is electrically connected with the direct-current capacitor, and the direct-current capacitor provides smooth direct-current voltage for the H-bridge current converter; the filter is connected in series with the H-bridge current converter, the bypass switch is connected in parallel with the H-bridge current converter, and the metal oxide voltage limiter is connected in parallel with the line side output end of the ice melting sub-module; and the ice melting sub-modules adjust the current of the corresponding split sub-conductors by changing the equivalent impedance of the ice melting sub-modules, so that accurate ice melting of the ice-coated split sub-conductors is realized, and the overall current and the transmission power of the power transmission line are kept unchanged. The technical problem to be solved by the invention is to provide the distributed ice melting device topological structure suitable for the ultra-high voltage power transmission line, and the technical problem that the existing ice melting technology cannot realize accurate ice melting and non-power-cut operation on an ice coating section on the ultra-high voltage power transmission line is solved. And normal transmission of the line is affected due to overlarge capacity demand, line overcurrent or incapability of three-phase synchronous ice melting.

The application provides an Ethernet-based linear series monitoring system and related equipment, the linear series monitoring system comprising a host device and a plurality of slave devices, a main power supply tap being led out from a secondary coil of each first coupling transformer, and an output end of a first power supply unit being connected with each main power supply tap; a primary tap being led out from a primary coil of each second coupling transformer, and a secondary tap being led out from a secondary coil of each third coupling transformer, a primary tap of an nth second coupling transformer in the same slave device being connected with a secondary tap of an nth third coupling transformer; and the primary taps of the N second coupling transformers in the same slave device all being connected with an input end of a rectifier unit. After the first power supply unit starts to supply power, parallel power supply is performed through 2N wires, so that the equivalent comprehensive line resistance is reduced, the voltage drop and loss are reduced, and the stability of line power supply is improved.

The invention discloses a differential derivative structure circuit based on three-coupling transformation and an amplifier, and relates to the technical field of amplification circuit design. The differential derivative structure circuit comprises a three-coupling inductance network and N output parts. Through a three-coupling transformation mode, power supply of a main amplifier tube and an auxiliary amplifier tube in a differential derivative structure formed by connecting MOS tubes in parallel is integrated into an inductance matching network, so that homologous coupling of the main amplifier tube and the auxiliary amplifier tube on a radio frequency signal path is realized, physical isolation and independent bias control are also realized on a direct current path, and the power supply efficiency is improved. Therefore, a resistor does not need to be used, excessive use of a capacitor is avoided, loss caused by self impedance of the capacitor and ground parasitic capacitance loss are reduced, gain is greatly improved, extra area occupation caused by the capacitor and the resistor is effectively inhibited, and thermal noise introduced by the resistor is eliminated by utilizing the characteristic of low impedance of inductive coupling. Therefore, post-stage noise is effectively suppressed, and the noise coefficient is reduced.

This application belongs to the field of wireless charging technology, specifically relating to a constant current and constant voltage wireless charging system and method based on a three-coil loosely coupled transformer, including an inverter circuit, a primary-side compensation circuit, a resonant circuit, a secondary-side compensation circuit, a rectifier circuit, and a filter capacitor; the resonant circuit has an anti-parallel coil structure, with the third coil located on the secondary side and a single coil on the primary side; its advantages are high misalignment tolerance, load-independent output, and high efficiency.

This utility model discloses an industrial and commercial energy storage system based on PLC communication, including a power supply module. At least one PLC master node module and multiple PLC slave node modules are connected to the power supply module. The PLC master node module is connected to an EMS system via UART and GPIO, with the GPIO serving as an emergency response port. Multiple functional modules are connected to each of the multiple PLC slave node modules. A coupling transformer is installed between the PLC master node module and the multiple PLC slave modules and the power line to establish a communication channel. By utilizing existing power cables as the communication medium, this completely changes the traditional "one module, one cabling" model of energy storage systems, drastically reducing the number of communication cables within industrial and commercial energy storage equipment and significantly shortening cabling time.

The invention discloses a start-stop control method for an impedance test power supply of a new energy grid-connected converter, and belongs to the technical field of power electronic test. According to the method, specific to the safety problems of overvoltage, impact current and the like which are easily generated in the switching process of the impedance test power supply based on the open winding structure of the broadband coupling transformer, the detailed switching-out logic of the starting logic sum is designed. According to the control method, the action time sequence of a low-voltage switch K1, a short-circuit switch K2 and a relay K3 is controlled in a coordinated mode, a follow current resistor R and a zero vector buffering technology are combined, and potential safety hazards such as high voltage and impact current generated in the test power supply starting and switching-out process are avoided; and meanwhile, a quasi-proportional resonance (QPR) control algorithm is adopted, so that the accuracy of broadband impedance measurement is ensured. According to the invention, the core defect of lack of switching safety control in the prior art is made up, high safety and reliability of the test process are realized, and the method is suitable for impedance characteristic test of various new energy grid-connected converters.

The application belongs to the technical field of wireless communication, and relates to an amplifier of a radio frequency front end in a transceiving system, and particularly provides a bidirectional amplifier based on an LMBA structure and three coupled transformers, which is used to improve the PA efficiency of the bidirectional amplifier and reduce the LNA noise coefficient; the three coupled transformers are adopted, the replacement of switches is realized by using the impedance characteristic change of a transistor, compared with the bidirectional amplifier structure with switches, the bidirectional amplifier has lower insertion loss in the radio frequency field, the improvement of the PA efficiency of the bidirectional amplifier and the reduction of the LNA noise coefficient are realized; meanwhile, the PA adopts the LMBA structure, the bidirectional amplification of signals is realized by using a BA path, compared with the previous bidirectional amplifier, the bidirectional amplifier has the characteristics of high efficiency in the power backoff interval.

The invention belongs to the technical field of voltage regulation devices, and particularly relates to a power electronic voltage regulation device and method with a voltage grouping regulation function, and the device comprises a circuit breaker QF1, a bypass assembly and two voltage regulation assemblies. The power supply is connected with the input end of the circuit breaker QF1; the output end of the circuit breaker QF1 is divided into three paths which are respectively connected with the bypass assembly and the two voltage regulating assemblies; the two voltage regulating assemblies respectively comprise a coupling transformer T1 with a first transformation ratio and a coupling transformer T2 with a second transformation ratio; wherein the second transformation ratio is greater than the first transformation ratio. Output of voltage and current is adjusted in a grouping mode through the coupling transformer, the first transformation ratio transformer is adopted when the small voltage adjusting requirement is met, the second transformation ratio transformer is adopted when the large voltage adjusting requirement is met, and therefore the voltage adjusting range of the electronic voltage adjusting circuit can be reduced to a reasonable value. Therefore, a relatively high voltage regulation range and relatively low installation capacity are realized at the same time, and the workload of the electronic voltage regulation circuit is reduced.

The application discloses a large-section conductor alternating current resistance automatic testing system and method, and relates to the electrical testing field.The system comprises a computer, an FPGA / real-time system, a D / A converter 1, a D / A converter 2, a D / A converter 3, an A / D converter, a voltage-controlled current source, electrodes, a GIL conductive pipe sample, a through-type high-precision current transformer, a high-precision resistor R, a lock-in amplifier and a coupling transformer with a load Z.The application eliminates the mutual inductance between a current loop and a voltage testing loop and the influence of the self-inductance of a sample, generates a 90-degree leading current voltage based on an equivalent circuit model through the FPGA and the D / A converter, and is used for compensating the voltage on the self-inductance of the sample and the mutual inductance in the voltage testing loop, reducing the phase angle between the voltage on the measured conductor and the exciting current, solving the precision problem of the large-section conductor alternating current resistance testing, and realizing the accurate and automatic measurement of the large-section conductor alternating current resistance.

First and second converters comprise an input and a switching bridge comprising a pair of switches coupled in series via a common node and coupled in parallel with the input. The second converter is coupled in series with the first converter via a common converter node. A transformer comprises a first balance winding coupled in series with a first primary winding via a first current flow path and a second balance winding coupled in series with a second primary winding via a first current flow path. The first current flow path is coupled in series with the first common node, and the second current flow path is coupled in series with the second common node.

The application provides a multi-stage wireless power supply coupling transformer, and relates to the technical field of power electronics, and comprises a plurality of stages of transformer modules connected in sequence, one stage of the transformer modules comprises one IGBT and one transformer connected in sequence, the transformer comprises an isolation coil, a power supply coil, a resonance capacitor, a core and a driving circuit, the core is wound with a first isolation coil and a second isolation coil from top to bottom on two longitudinal edges of the core, the first isolation coil and the second isolation coil are used to transmit electric energy of each stage, the core is wound with the power supply coil on one transverse edge of the core, the power supply coil is connected with the driving circuit, the driving circuit is connected with the IGBT and controls the conduction and the turn-off of the IGBT, compared with the traditional transformer, the multi-stage wireless power supply coupling transformer can realize multi-directional electric energy transmission, the resonance capacitor is added to eliminate leakage inductance, the compatibility is high, the volume is small, and the insulation strength of the coil increases with the increase of the stage number.

This invention discloses a nested TLVR multiphase voltage regulator and its control method to solve the problems of large size of coupling transformers, high AC magnetic flux density and core loss, long interconnection lines of coupling windings, complex interconnection of coupling windings, and high conduction loss of interconnection circuits in existing TLVR multiphase voltage regulators. Through the nested TLVR structure, this invention allows the coupling transformer to be interconnected only with adjacent or nearby coupling transformers, reducing the complexity of coupling transformer winding interconnection, the length of interconnection circuits, and losses. This invention can also effectively reduce the inductance of the coupling transformer itself, reduce the peak AC magnetic flux and core loss of the coupling transformer core, thereby effectively reducing the size and losses of the coupling transformer. This invention provides a simpler, easier-to-implement, more efficient, and higher power density solution for multiphase voltage regulators supplying power to various computing processor chips.

The invention provides a modularized multi-level flexible interconnection topology based on a magnetic coupling transformer and a low-frequency power elimination strategy of the modularized multi-level flexible interconnection topology, and aims to solve the problems that sub-modules in a flexible interconnection system of a medium-voltage power distribution network are large in capacitance and low-frequency power fluctuation is remarkable. In order to solve the problem that the requirement for a sub-module capacitor is large, a six-active-bridge magnetic coupling transformer structure is introduced, three-phase power is gathered in a magnetic coupling loop and counteracts the three-phase power, and therefore low-frequency voltage fluctuation of the sub-module capacitor is remarkably weakened. And a low-frequency power elimination control strategy is further adopted, so that the equivalent impedance at the position of the system is remarkably reduced, and the low-frequency power mainly flows through the MCTSAB instead of the capacitor. According to the topology, the output voltage can still be kept stable under the condition that the capacitance value is reduced by 90%, low-frequency ripples are effectively restrained, and a feasible scheme is provided for a flexible interconnection system of a medium-voltage power distribution network.

The application discloses a C-shaped iron core combined rotary loose coupling transformer, which comprises a fixed assembly and a rotary assembly. The fixed assembly comprises a fixed iron core, first and second fixed windings and a fixed side circuit; the longitudinal section of the fixed iron core is in the shape of a C letter, and the fixed iron core comprises a first fixed iron core, a second fixed iron core and a third fixed iron core; the rotary assembly comprises a rotary magnetic core, a rotary shaft, a rotary bearing, a rotary clamping groove, first and second radial rotary rings, first and second rotary windings and a rotating side circuit; the fixed iron core surrounds the outer periphery of the rotary shaft in the radial direction, and the fixed iron core and the rotary shaft are fixed by the rotary bearing; the first fixed winding and the second fixed winding are connected in series, and the first rotary winding and the second rotary winding are also connected in series. The C-shaped iron core combined rotary loose coupling transformer designed by the application reduces the axial size and weight, improves the power transmission capacity, and first connects the rotating side circuit with a matrix converter.

This invention discloses a broadband multi-coupled millimeter-wave band low-noise amplifier, comprising an input matching network, an inter-stage matching network, an output matching network, and two-stage amplifier transistors. The two-stage amplifier transistors include a common-source amplifier transistor located on the signal input side and a common-gate amplifier transistor located on the signal output side. The input terminal of the common-source amplifier transistor is connected to the output terminal of the input matching network. The inter-stage matching network connects the output terminal of the common-source amplifier transistor to the input terminal of the common-gate amplifier transistor. The output terminal of the common-gate amplifier transistor is connected to the input terminal of the output matching network. This invention achieves area reuse of the source and gate inductors based on a three-coupling transformer matching network, significantly reducing the chip area and possessing significant practical value.

The application relates to a high-precision frequency tracking device and method for rotary ultrasonic auxiliary machining, and the tracking device comprises a microcontroller, an upper computer, a signal generating module, a power amplification module, a compensation circuit, a loosely coupled transformer, a dynamometer, a sampling module and a signal conditioning module; the microprocessor is connected with the upper computer, the signal generator module, a first band-pass filter circuit and a second band-pass filter circuit respectively; the signal generating module is connected with the power amplification module; the power amplification module is sequentially connected with a voltage sensor and a primary side of the loosely coupled transformer; the dynamometer measures the cutting force in the machining process, and the counterforce of the force is a load force received by a transducer. The application fully considers the problem that static matching failure caused by load force change in the rotary ultrasonic machining process further leads to the decline of frequency tracking precision, and improves the frequency tracking precision. The application has the advantages of low cost, fast frequency tracking speed, high precision and strong adaptability.

The utility model belongs to the technical field of electric power engineering, and relates to a multi-signal source cascade high-efficiency power synthesis circuit based on transformer coupling, which comprises a signal generator and a plurality of broadband power amplification branches connected in parallel, each broadband power amplification branch has the same structure and comprises a signal amplifier, a coupling transformer and an impedance tuning circuit which are connected in sequence; the impedance tuning circuit adopts an L-C circuit; the output ends of the impedance tuning circuits of the broadband power amplification branches are connected in sequence, and the output ends of the impedance tuning circuits of the first broadband power amplification branch and the last broadband power amplification branch serve as the output end of the multi-signal-source cascade efficient power synthesis circuit. According to the high-power signal source output circuit, efficient synthesis of multiple paths of signals can be achieved through multi-stage amplification, and the high-power signal source output circuit is safe, simple and efficient.

The utility model discloses a voltage regulation circuit and a power supply, and relates to the technical field of circuits. After the boost-buck converter supplies power, the purpose of changing the output voltage of the output end of the boost-buck converter is achieved after the output voltage of the controller voltage regulating circuit, the voltage of the output end of the boost-buck converter and the first resistor, the second resistor and the third resistor act on a feedback pin of the boost-buck converter; the output voltage of the power adapter is generally smaller than the voltage of the mains supply, so that the potential safety hazard of the adjustable power supply to a human body can be reduced by adjusting the voltage based on the power adapter, a coupling transformer and the like are not needed, and the cost is reduced; and the configuration end of the power adapter is connected with the output end of the power protocol communication processing circuit, so that the power adapter can output relatively high voltage for the boost-buck converter to use, and under the condition of keeping the same power transmission, the high voltage transmission can reduce the magnitude of current, thereby reducing the line and energy loss and improving the transmission efficiency.

The application provides a carrier communication network noise absorption system, which comprises a power supply unit for supplying power for the system, a noise and PLC signal coupling unit for accessing a power line, a coupling capacitor and a coupling transformer circuit for filtering and outputting noise and PLC signals in the power line, and a PLUS pulse signal for reflecting whether the signal in the power line is a valid PLC signal according to the leading wave characteristics of the PLC signal package header; a noise absorption unit connected with the noise and PLC signal coupling unit, for applying different loads on the noise source of the power line, so that the noise energy is converted into heat energy and the noise voltage amplitude is reduced; and a PLC signal analysis unit connected with the noise and PLC signal coupling unit and the noise absorption unit, for performing peak value sampling on the noise and PLC signals output by the noise and PLC signal coupling unit, judging whether the current signal is a PLC signal or a noise signal, and controlling different loads to absorb the noise.

The invention relates to the technical field of power systems, and discloses a grid-connected grounding topological structure of a flexible converter device without a connection transformer, which is based on a topological structure that a far-end three-winding transformer and a Z-type transformer are grounded through a small resistor. The problem that a three-phase alternating-current circuit breaker is difficult to quickly and completely switch off and switch on when a non-connection transformer is matched with a traditional arc suppression coil to be grounded can be solved. When a single-pole grounding fault occurs on the direct current side of the flexible device matched with the uncoupled transformer system, a large amount of direct current bias current on the side of the flexible device flows into the alternating current network side due to the fact that no coupled transformer exists between the alternating current network and the flexible device, and the topological structure can greatly reduce the influence of the direct current bias current on the three-phase alternating current circuit breaker at the moment. And each phase of the three-phase circuit breaker at the alternating current side can be quickly and completely switched off and switched on. In addition, the topological structure can limit the peak value of the fault current on the alternating current side when the system has a single-pole grounding fault on the direct current side.

The application discloses an analog encryption telephone terminal based on transmission of a public switched telephone network, and relates to the technical field of analog communication, comprising an analog line interface module, an analog voice module, a power filter module, a power supply control module, an encryption processing module, a signal coupling and isolation module, a ringing detection module and a man-machine interaction module. The method directly controls the on-off safety encryption chip power supply and the enable pin of the NMOS tube through a pure hardware switch of a physical encryption key, and realizes external independent power supply and signal coupling transformer isolation direct current, so that the technical problems of the existing analog encryption telephone, such as dependence on software control, bypassing, poor reliability of mechanical relay switching and inability of the key to be completely physically destroyed after hanging up, are solved.