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First, the resistance

The resistance is represented by "R" plus a number in the circuit. For example, R1 means that the main resistance of the resistor with the number 1 is shunt, current limit, voltage division, offset, etc. 1. Parameter identification: the unit of resistance is ohm (Ω), the unit of magnification is: kilo ohm (KΩ), megohm (MΩ), etc.

The conversion method is: 1 megaohm = 1000 kilo ohms = 1000000 ohms. There are three kinds of parameter labeling methods, namely, the direct label method, the color scale method and the number standard method. The number standard method is mainly used for small-sized circuits such as patches. For example, 472 means 47×100Ω (ie 4.7K); 104 means 100Kb, color ring labeling method is the most used, now as an example: four color ring resistance five color ring resistance (precision resistance)

2. The relationship between the color mark position and the magnification of the resistor is shown in the following table: Color Effective Digital Magnification Allowable Deviation (%) Silver / x0.01 ±10 Gold / x0.1 ±5 Black 0 +0 / Brown 1 x10 ±1 Red 2 X100 ± 2 orange 3 x 1000 / yellow 4 x 10000 / green 5 x 100000 ± 0.5 blue 6 x 1000000 ± 0.2 purple 7 x 10000000 ± 0.1 gray 8 x 100000000 / white 9 x 1000000000

Second, the capacitor

1. The capacitor is generally represented by “C” plus a number in the circuit (for example, C13 indicates the capacitor numbered 13). The capacitor is composed of two metal films close to each other, and the characteristics of the component capacitors separated by insulating materials are mainly separated. The size of the DC-AC AC capacitor is the size of the energy that can be stored. The blocking effect of the capacitor on the AC signal is called the capacitive reactance. It is related to the frequency and capacitance of the AC signal. The capacitive reactance XC=1/2πf c (f indicates the AC signal. Frequency, C indicates the capacity of the capacitor. The types of capacitors commonly used in telephones are electrolytic capacitors, ceramic capacitors, chip capacitors, monolithic capacitors, tantalum capacitors, and polyester capacitors.

2, identification method:

The identification method of the capacitance is basically the same as the identification method of the resistance. The basic unit usage (F) of the three types of capacitances, such as the direct label method, the color scale method and the digital standard method, is expressed by other methods: milli-method (mF), micro-method (uF), nanofarad (nF), picofarad (pF) where: 1 Farad = 103 millifarads = 106 microfarads = 109 nanofarads = 1012. Capacitance capacity is large. The capacitance value is directly indicated on the capacitor, such as 10 The capacitance of a small capacity of uF/16V capacity is represented by letters or numbers on the capacitance. The letter representation: 1m=1000 uF 1P2=1.2PF 1n=1000PF Digital representation: generally three digits are used to indicate the capacity, the first two digits Indicates a significant digit, the third digit is the magnification such as: 102 indicates 10 × 102 PF = 1000 PF 224 indicates 22 × 104 PF = 0.22 uF3, capacitance capacity error table symbol FGJKLM tolerance ± 1% ± 2% ± 5% ± 10% ± 15 % ± 20% such as: a ceramic capacitor of 104J indicates a capacity of 0. 1 uF, an error of ± 5%

Third, the crystal diode

The crystal diode is usually represented by a "D" plus a number in the circuit, such as: D5 represents a diode numbered 5

1, role:

The main characteristic of the diode is unidirectional conductivity, that is, the on-resistance is small under the action of the forward voltage; and the on-resistance is extremely large or infinite under the action of the reverse voltage. Because the diode has the above characteristics, the cordless telephone It is often used in rectifier, isolation, voltage regulation, polarity protection, code control, FM modulation and squelch circuits. The crystal diodes used in telephones can be divided into: rectifier diodes (such as 1N4004), isolation diodes ( Such as 1N4148), Schottky diode (such as BAT85), LED, Zener diode, etc.

2, identification method:

The identification of the diode is very simple. The N pole (negative) of the small power diode is mostly marked with a color circle on the outer surface of the diode. Some diodes also use the diode-specific symbol to indicate the P pole (positive pole) or the N pole (negative pole). The positive and negative LEDs of the LEDs with the symbol marks "P" and "N" to determine the polarity of the diode can be identified by the length of the pin. The long leg is positive and the short leg is negative 3. Test Note: Using a digital multimeter When measuring the diode, the red pen is connected to the positive pole of the diode, and the black test lead is connected to the negative pole of the diode. The resistance measured at this time is the forward conduction resistance of the diode, which is exactly the opposite of the pointer connection of the pointer multimeter. The 1N4000 series diode withstand voltage is compared as follows: Model 1N4001 1N4002 1N4003 1N4004 1N4005 1N4006 1N4007 withstand voltage (V) 50 100 200 400 600 800 1000 current (A) are 1

Fourth, the Zener diode Zener diode

In the circuit commonly used "ZD" plus a number, such as: ZD5 represents the number 5 regulator

1, the regulator of the Zener diode

Principle: The characteristic of the Zener diode is that after the breakdown, the voltage at both ends remains basically the same. When the voltage regulator is connected to the circuit, if the voltage of the circuit changes due to fluctuations in the power supply voltage or other reasons, , the voltage across the load will remain essentially the same

2. Fault characteristics: The fault of the Zener diode is mainly manifested in open circuit, short circuit and unstable voltage regulation. Among the three kinds of faults, the former fault shows that the power supply voltage rises; the latter two faults show that the power supply voltage is low. The model and regulation value of the commonly used Zener diode to zero volt or output instability are as follows: Model 1N4728 1N4729 1N4730 1N4732 1N4733 1N4734 1N4735 1N4744 1N4750 1N47511N4761 Regulatory value 3.3V 3.6V 3.9V 4.7V 5.1V 5.6V 6.2V 15V 27V 30V 75V