Loudspeaker

Loudspeakers name suggests is the sound amplification, spread farther mean relatively speaker, microphone sound more penetrating.
Loudspeaker according to its size, usage and purpose can be divided into various types, each with their use advantage. Due to the shape and size of portable loudspeakers, speakers’ constraints, general power is only 3--8W. The wireless microphone wired microphone and volume sizes are various different purposes, and smaller size for teachers, tour guides used to hang at the waist, both hands to play more freely, its power is generally also 3W-8W. Bulky for outdoor activities, summer camps, extracurricular lectures and other high traffic areas, the power at 35W --- 95W. Lithium battery according to the type of loudspeaker is made using a classification. It solves the problem of pollution on the environment of traditional batteries, which is used mainly in the mobile phone supply lithium-ion technology to the loudspeaker.

Traditional loudspeakers, through universal, homogeneous competition in recent years, have brought the market price shopping, so that companies are increasingly emphasis on cost rather than quality. Blind pursuit of cost, not only contribute to sound quality cannot be improved, but also makes noise noise increases, to bring a certain degree of physical and mental damage to the user.

Poor sound quality, cannot meet the standard of living has been increasing gradually increasing consumer demand, the market needs to product upgrades. The new "sub-spreader" because the use of crossover broadcast technology to effectively solve the traditional loudspeaker sound rushed, fried, thick, shortcomings. You can enhance the soft and delicate, reduce noise, so sound quality is more stress. The audience does not cause dizziness, irritability, rapid heartbeat, high blood pressure, and entertainment at the same time to feel more pleasure, more physical and mental health. Sub-spreader enables high bass harmony echo, microphone input sound, but also can play a more realistic sound, so seize the audience, enhance the sense of affinity.

Hybrid integrated circuits

Hybrid integrated circuits are then integrated semiconductor integrated circuit external components, or said secondary integration. It is composed of a semiconductor integrated process and thick (thin) film technology combined and integrated circuits made of semiconductor integrated circuits, it is also one of the miniaturization of electronic equipment, the main way to achieve.

Hybrid integrated circuits including the thick-film, hybrid integrated circuits and thin film, thick-film hybrid integrated circuits. Thick-film hybrid integrated circuits is an insulating substrate (typically ceramic) as the substrate of the circuit, and the first conductor network resistance, capacitance and other components using serigraphy, plasma spraying and other craft printed on the substrate surface, then use the WB, TAB , FCB and reflow soldering and other processes, the other components (such as integrated circuits, sensors, other functional elements, etc.) assembled on a ceramic substrate, and then connect the output pin, and finally as a whole package, the formation of a fully functional circuit products. Known as a thick film integrated circuit or directly called thick.

Film hybrid integrated circuit is the use of thin-film vacuum deposition techniques, sputtering, photolithography and other basic process, the electronic components of the circuit in the form of film products in the production of circuits formed on an insulating substrate.

Programmable DC Electronic Load

Programmable DC Electronic Load is the principle of the flux guide or the control of the power MOSFET transistors (duty ratio of the size of the volume), the power dissipated by the power consumption of the power tube apparatus which can accurately detect the load voltage, load current precise adjustment, while analog load short-circuit, an analog resistive and inductive load is capacitive, capacitive load current rise time. Debugging detect general switching power supply is indispensable.

Programmable DC electronic load can simulate real-world loads (appliances). It has a constant current, constant resistance, constant voltage and constant power capabilities, as well as short circuit, over current, dynamic, etc., it should be said that all power manufacturers will be useful, but also must have. Electronic load into DC electronic load and AC electronic load, electronic load due to the application surface problem, this paper introduces the DC electronic loads.

1. Voltage, current and power of choice

According to the output characteristics of the device under test to select electronic load: voltage, current, power and accuracy of the testing requirements. Programmable DC Electronic Load Module can only work when tested alone or parallel operation, the series for the module is very dangerous. So ideal state is that all requirements are within the range single group, followed by multiple modules connected in parallel to achieve the selection. That is, when the voltage of the selected module must meet the test requirements. Individual modules or the full sum of the current and power box is installed to meet the testing requirements.

2. Accuracy and resolution choices

Accuracy and resolution is an important parameter index electronic load. Meaning accuracy of different representations of programmable DC electronic load.

Capacitors

Capacitor referred capacitors; it is also a major element of the electronic circuit components. It can store electrical energy, with the charge, discharge and through the exchange, DC-blocking properties. In a sense, a bit like a capacitor battery. Although both work in very different ways, but they can store energy.

Battery has two electrodes inside the battery, so that a chemical reaction to produce electron electrode, the other electrode of the electron absorption. The capacitor will have a much simpler, it does not produce electron - it just to store electrons. It is one of the indispensable basic elements of the extensive use of various types of electronic equipment. Various capacitors in the circuit can play different roles, such as coupling and DC blocking, bypass, rectifier filter, high-frequency filter, tuning, storage and division and so on. The capacitor should be selected according to the circuit voltage, frequency, waveform, AC and DC components of temperature and humidity conditions.
Capacitor, typically referred to its ability to hold a charge capacitance, denoted by the letter C.   Capacitors, by definition, is 'loaded container electricity', it is a device receiving the charge. English name: capacitor. Capacitor is one of a large number of electronic components used in electronic equipment; it is widely used in the circuit compartment straight cross-connection, coupling, bypass, filtering, tuning circuits, energy conversion and control.

The capacitance of the capacitor is different. Capacitance basic physical quantities, the symbol C, the unit is F (farad).

General formula C = Q / U parallel plate capacitor special formula: electric field strength between the plates E = U / d, the capacitor capacitance of the formula C = εS / 4πkd.

Amplitude modulation

Amplitude modulation (AM) also referred to as amplitude, by varying the amplitude of the output signal, to achieve the purpose of transmitting information. General changes in the amplitude modulation of the high-frequency end of the output signal and the original signal into a certain function, demodulation end demodulates and outputs the original signal.

In fact, a function is generally proportional relationship. The greatest benefit of this modulation is the modulation and demodulation is very simple, just a diode and a capacitor can, of course, the biggest drawback is the relatively large distortion, while more sensitive to interference, relatively speaking, is a relatively old technology. But technology does not mean that the old applications are not widespread, there are still many areas of application, such as a radio (AM radio) and Aeronautical Radio, Especially in the field of aviation radio, the traveling speed of the aircraft very quickly, quicker fighter, for FM, the Doppler effect is too big, it will affect communications, and AM is not affected by the Doppler effect, it can not be replaced. At the same time there are some improvements AM techniques, such as single sideband modulation (also known as single sideband), residual sideband modulation (Vestigial Side Band, VSB), and amplitude modulation multiple variants such as the current amplitude is widely used in a mobile communication digital modulation.

Dipole antenna

Dipole antenna used to transmit and receive signals of fixed frequency. Although the usual measurements are used in wideband antenna, but the venue and the measurement antenna attenuation coefficients are required to use a dipole antenna. Dipole antenna in the frequency range 30MHz ~ 4GHz. Which is a set of precise VHAP and UHAP dipole antenna is especially suitable for measuring site attenuation and antenna factor. Meanwhile, the antenna for the Japanese VCCI standards organizations designated only dedicated antenna anechoic chambers and open-field site attenuation measurement and the like. The antenna is used by many laboratories, as antenna standard laboratories.

Vertical antenna is actually a dipole antenna. Dipole antenna consists of two conductors, each 1/4 wavelength, i.e., the total length of a half wavelength of the antenna. So dipole antenna, also called half-wave dipole. The transducer can be a dipole antenna horizontal position, vertical position may be. Its pattern to the feeding point of symmetry. Feed point in the center of the half-wave vibrator. Feed point impedance is purely resistive, approximate 75Ω (approximately 73Ω). If the two 1/4 wavelength resonator extended and then folded back to the center, and joined together, then it became a folded dipole antenna, referred to as folded vibrator.

Folded dipole antenna impedance is purely resistive approximate 300Ω (about 290Ω), shows a high input impedance, high impedance transmission antenna feeder parallel constitute use in many occasions. The dipole antenna straight up, perpendicular to the ground, then a vertical antenna. If the "remove" the lower part of the 1 / 4λ oscillator, the asymmetrically vertical antenna. Common vertical antenna are asymmetric antenna, isotropic in the horizontal direction.
A special.This antenna has a special name called Marconi antenna. R7000 receiver and other antenna configurations belong to this antenna.

Battery

Battery, defined in a narrow sense is itself generally stored chemical energy into electrical energy device, broadly defined as pre-stored energy from the device into external power available. So, like solar conversion without storage function only means not a battery. Other names have batteries, batteries, and Chinese have storage tanks and bottles intended effect.
Historical battery can be traced back two thousand years ago in ancient Iraq era. In the capital Baghdad found unglazed clay pots. It is a copper and iron battery.
Type of Batteries

Chemical batteries, electrochemical cell means by an oxidation-reduction reaction, the positive electrode, a negative electrode active material of chemical energy, into electrical energy for a class of devices. Common redox reaction with different oxidation and reduction reactions that are carried out separately, the oxidation of the negative electrode, the reduction in the positive electrode, and the electron gains and losses is carried out by an external circuit, thus forming a current.

Dry and liquid batteries distinguish battery is limited to that period of early development. The first battery of a glass container filled with an electrolyte and two electrodes. Later we introduced to paste electrolyte-based batteries, also known as dry batteries.

Disposable batteries (Primary Battery), commonly known as "disposable" cell, because after their power runs out, can not be recharged using only discarded. Common disposable batteries include:
Manganese battery - voltage of about 1.5V, the battery capacity is low, the battery can output low, almost alkaline manganese batteries are replaced, except after long-term storage is not leaking harmful corrosive liquids, so still in use in low electricity requires long-term use of devices simultaneously, such as clock, infrared remote control and so on.
Alkaline manganese battery - voltage of about 1.5V, battery capacity and output of the battery than the zinc-manganese batteries is high, but less than nickel-metal hydride battery, after long-term storage of hazardous leaking corrosive liquids.

Other disposable batteries include zinc batteries, zinc-air battery, zinc-mercury batteries, mercury batteries, battery and magnesium hydroxide, manganese batteries.
Rechargeable batteries, also known as the secondary battery (Secondary battery), batteries. Rechargeable battery according to different production materials and workmanship, the advantage can be reused many times after it is charged, they can be full charged and discharged more than two times or even up to 2500, the rechargeable battery output current (load force) than large part disposable batteries is high. Common types are:

Lead-acid battery - voltage of about 12V, low capacity, but can output more power, battery, often used in automobiles for starting the engine to use, or for uninterruptible power system (UPS), radios, communications machine.