SEZ electrical components Germany SEZ model SEZ price

SEZ electrical components refer to the aggregate of service equipment provided for a specific group of traffic sources, such as trunk lines, switching devices, control systems, etc. The fundamental research content of traffic theory is the relationship among traffic volume, call loss, and bundle capacity; therefore, the bundle is an important basic concept in traffic theory. A traffic source is the service object of a bundle, usually referring to user equipment; broadly speaking, the upper-level equipment is the traffic source for the lower-level equipment. In telephone communication, a traffic source is also called a call source. The number of service devices contained in a bundle is called the bundle capacity. Figure 1 is a schematic diagram of a bundle. The capacity of this bundle is V, and it provides service for N traffic sources. Any traffic source initiating a call can occupy an idle service device in the bundle.

SEZ electrical component characteristics

(1) volt-ampere characteristics: When a forward voltage is applied to a diode, if the voltage value is small, the current is extremely small; when the voltage exceeds a certain value, the current begins to increase exponentially. This is usually called the turn-on voltage of the diode. When the diode is in a fully conductive state, this voltage is usually called the conduction voltage of the diode. For germanium diodes, when a reverse voltage is applied to the diode, if the voltage value is small, the current is extremely small, and its current value is the reverse saturation current. When the reverse voltage exceeds a certain value, the current increases sharply, which is called reverse breakdown, and this voltage is called the reverse breakdown voltage of the diode. The breakdown voltage values of different diode models vary greatly, from tens of volts to thousands of volts. (2) Forward characteristics: When a forward voltage is applied, in the initial part of the forward characteristics, the forward voltage is very small and insufficient to overcome the blocking effect of the electric field within the PN junction, so the forward current is almost zero. This section is called the dead zone. The forward voltage that cannot make the diode conduct is called the dead zone voltage. When the forward voltage is greater than the dead zone voltage, the electric field within the PN junction is overcome, the diode conducts in the forward direction, and the current rises rapidly with increasing voltage. Within the normal operating current range, the terminal voltage of the diode during conduction remains almost constant; this voltage is called the forward voltage of the diode. When the forward voltage across the diode exceeds a certain value, the internal electric field is quickly weakened, the characteristic current grows rapidly, and the diode conducts in the forward direction. This is called the threshold voltage or cut-in voltage. (3) Reverse characteristics: When the applied reverse voltage does not exceed a certain range, the current flowing through the diode is a reverse current formed by the drift motion of minority carriers. Since the reverse current is very small, the diode is in the cutoff state. This reverse current is also called reverse saturation current or leakage current. The reverse saturation current of a diode is greatly affected by temperature. Generally, the reverse current of silicon tubes is much smaller than that of germanium tubes. The reverse saturation current of low-power silicon tubes is on the order of nA, and that of low-power germanium tubes is on the order of μA. When the temperature rises, the semiconductor is thermally excited, the number of minority carriers increases, and the reverse saturation current also increases. (4) Breakdown characteristics: When the applied reverse voltage exceeds a certain value, the reverse current suddenly increases. This phenomenon is called electrical breakdown. The critical voltage causing electrical breakdown is called the diode reverse breakdown voltage. During electrical breakdown, the diode loses its unidirectional conductivity. If the diode does not overheat due to electrical breakdown, the unidirectional conductivity will not necessarily be permanently destroyed. After removing the applied voltage, its performance can still recover; otherwise, the diode will be damaged. Therefore, excessive reverse voltage applied to the diode should be avoided during use. Reverse breakdown is divided into two types based on mechanism: Zener breakdown and avalanche breakdown. In cases of high doping concentration, because the width of the barrier region is very small, a large reverse voltage destroys the covalent bond structure within the barrier region, causing valence electrons to break free from covalent bonds and generate electron-hole pairs, resulting in a sharp increase in current. This type of breakdown is called Zener breakdown. If the doping concentration is low and the barrier region is wide, Zener breakdown is not easy to occur. Another type of breakdown is avalanche breakdown. When the reverse voltage increases to a large value, the external electric field accelerates the drift speed of electrons, causing them to collide with valence electrons in covalent bonds, knocking valence electrons out of covalent bonds and generating new electron-hole pairs. The newly generated electron-hole pairs are accelerated by the electric field and knock out other valence electrons, causing an avalanche-like increase in carriers and a sharp increase in current. This type of breakdown is called avalanche breakdown. Regardless of the type of breakdown, if the current is not limited, it may cause permanent damage to the PN junction. (5) Reverse current: Reverse current refers to the current flowing through the diode when it is subjected to ambient temperature and the maximum reverse voltage. The smaller the reverse current, the better the unidirectional conductivity of the tube. It is worth noting that reverse current is closely related to temperature; the reverse current doubles. Therefore, silicon diodes have better stability at high temperatures than germanium diodes. (6) Dynamic resistance: The ratio of the change in voltage to the corresponding change in current near the static operating point of the diode characteristic curve. (7) Voltage temperature coefficient: The voltage temperature coefficient refers to the relative change in stable voltage for every one degree Celsius increase in temperature. (8) Maximum operating frequency: The maximum operating frequency is the upper limit frequency for diode operation. Since the diode, like the PN junction, has a junction capacitance composed of barrier capacitance, the value of the maximum operating frequency mainly depends on the size of the PN junction capacitance. If this value is exceeded, the unidirectional conductivity will be affected. (9) Maximum rectified current: Maximum rectified current refers to the maximum allowable average forward current value when the diode operates continuously for a long period. Its value is related to the PN junction area and external heat dissipation conditions. Because current passing through the tube causes the core to heat up and the temperature to rise, exceeding the permissible limit will cause the core to overheat and become damaged. Therefore, under specified heat dissipation conditions, the diode should not exceed its maximum rectified current value during use.(10) Maximum reverse working voltage: When the reverse voltage applied across the diode reaches a certain value, the tube will break down and lose its unidirectional conductivity. To ensure safe operation, the maximum reverse working voltage value is specified.

SEZ electrical component structure

Common electrodynamic cone paper-cone loudspeakers. Electrodynamic cone loudspeakers were formerly known as paper-cone loudspeakers. Although the diaphragm is still primarily made of paper cone, many polymer material diaphragms and metal diaphragms have appeared, making the term cone loudspeaker more accurate. Cone paper-cone loudspeakers generally consist of three main parts: the magnetic circuit system (permanent magnet, core pole, magnetic plate), the vibration system (paper cone, voice coil), and the support auxiliary system (centering spider, basket, surround). 1. Voice coil: The voice coil is the drive unit of the cone paper-cone loudspeaker. It is made of very fine copper wire wound in two layers on a paper tube, typically with dozens of turns, also known as a coil. It is placed in the magnetic gap formed by the magnetic core pole and the magnetic plate. The voice coil is fixed to the paper cone. When an audio current signal is passed through the voice coil, the vibration of the voice coil drives the vibration of the paper cone. 2. Paper cone: There are many types of materials used for the cone diaphragm of cone paper-cone loudspeakers, generally divided into natural fibers and synthetic fibers. Natural fibers often include cotton, wood, wool, silk, etc., while synthetic fibers include rayon, nylon, fiberglass, etc. Since the paper cone is the sound radiation component of the loudspeaker, it largely determines the sound reproduction performance. Therefore, regardless of the type of paper cone, it must be lightweight and have good rigidity, and must not deform due to changes in ambient temperature or humidity. 3. Surround: The surround is designed to ensure axial movement of the paper cone along the loudspeaker axis and restrict lateral movement, while also preventing air flow between the front and back of the paper cone. In addition to materials commonly used for paper cones, surrounds utilize plastics, natural rubber, etc., bonded to the paper cone through hot pressing. 9. Centering spider: The centering spider supports the joint between the voice coil and the paper cone, ensuring it remains vertical and not skewed. The centering spider has many concentric rings, allowing the voice coil to move freely up and down in the magnetic gap without lateral movement, ensuring the voice coil does not touch the magnetic plate. The dust cap on the centering spider prevents external dust from falling into the magnetic gap, avoiding friction between dust and the voice coil, which could cause abnormal sounds from the loudspeaker. Generally, a loudspeaker consists of a magnet, frame, centering spider, molded surround, and cone paper cone.

SEZ electrical component types

1. Rotating thermometers are made of a coiled bimetallic strip. One end of the bimetallic strip is fixed, and the other end is connected to a pointer. Due to different expansion rates of the two metals, the degree of coiling of the bimetallic strip varies at different temperatures, causing the pointer to indicate different positions on the dial. The temperature can be determined from the reading on the dial. 2. The resistance change of semiconductor thermometers differs from that of metals; as temperature rises, their resistance decreases, and the magnitude of change is larger. Therefore, even small temperature changes can cause significant changes in resistance, resulting in thermometers with high precision, often called thermistors. 3. Thermocouple thermometers consist of two different metals connected to a sensitive voltmeter. At different temperatures, the metal junctions produce different potential differences at the ends of the metals. Since the potential difference is very small, a sensitive voltmeter is required to measure it. The temperature can be determined from the voltmeter reading. 4. Optical pyrometers: When an object's temperature is high enough to emit a large amount of visible light, its temperature can be determined by measuring the amount of thermal radiation. This type of thermometer is called an optical pyrometer. This thermometer mainly consists of a telescope equipped with a red filter and a circuit containing a small bulb, ammeter, and variable resistor. Before use, the relationship between the temperature corresponding to different filament brightness levels and the ammeter reading is established. During use, align the telescope with the object to be measured, adjust the resistance until the bulb's brightness matches that of the object, and then read the object's temperature from the ammeter. 5. Liquid crystal thermometers made with different formulations have different phase transition temperatures. When they undergo phase transition, their optical properties change, causing the liquid crystal to appear to change color. If liquid crystals with different phase transition temperatures are coated on a piece of paper, the temperature can be determined by the color change of the liquid crystal. The advantage of this thermometer is easy reading, while the disadvantage is insufficient accuracy. It is commonly used in ornamental fish tanks to indicate water temperature. 13. Digital thermometers use temperature sensors to convert (temperature) into digital signals, which are then displayed in numerical form on a display (such as LCD, digital tube, LED matrix, etc.). They can quickly and accurately measure the maximum human body temperature. Compared with traditional mercury thermometers, they offer advantages such as convenient digital reading, short measurement time, high measurement accuracy, memory function, and audible alerts. Especially since digital thermometers do not contain mercury, they are harmless to the human body and the surrounding environment, making them particularly suitable for use in hospitals and homes.

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