1. Resistance
The resistance is represented by "R" plus a number in the circuit, for example: R1 represents the resistance numbered 1. The main functions of resistance in the circuit are shunting, current limiting, voltage dividing, and bias.
1. Parameter identification:
The unit of resistance is ohm (Ω), the magnification unit is: kilo-ohm (KΩ), megohm (MΩ), etc. The conversion method is:
1 megohm = 1000 kohm = 1000000 euro
There are three kinds of resistance parameter labeling methods, namely direct standard method, color standard method and number standard method.
a. The digital scale method is mainly used for small-volume circuits such as patches, such as:
472 means 47 × 100Ω (ie 4.7K); 104 means 100K
b. The color circle labeling method is the most used. Examples are as follows:
Four-color ring resistance Five-color ring resistance (precision resistance)
2. The relationship between the color position of the resistor and the magnification is shown in the following table:
Permissible deviation of effective digital magnification of color (%)
Silver / x0.01 ± 10
Gold / x0.1 ± 5
Black 0 +0 /
Brown 1 x10 ± 1
Red 2 x100 ± 2
Orange 3 x1000 /
Yellow 4 x10000 /
Green 5 x100000 ± 0.5
Blue 6 x1000000 ± 0.2
Purple 7 x10000000 ± 0.1
Gray 8 x100000000 /
White 9 x1000000000 /
2. Capacitance
1. The capacitor is generally represented by "C" plus a number in the circuit (for example, C13 indicates the capacitor with the number 13). Capacitor is composed of two metal films close to each other, separated by an insulating material in the middle. The characteristics of the capacitor are mainly DC blocking AC.
The size of the capacitor capacity is the amount of energy that can be stored. The blocking effect of the capacitor on the AC signal is called capacitive reactance, which is related to the frequency and capacity of the AC signal.
Capacitance XC = 1 / 2Ï€f c (f represents the frequency of the AC signal, C represents the capacitance)
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 capacitor is basically the same as the identification method of resistance, which is divided into three types: straight standard method, color standard method and digital standard method.
The basic unit of capacitance is Farah (F), and other units are: millifarad (mF), microfarad (uF), nanofarad (nF), picofarad (pF).
Among them: 1 farad = 103 millifarad = 106 microfarad = 109 nanofarad = 1012 picofarad
The capacitance value of a large-capacity capacitor is directly marked on the capacitor, such as 10 uF / 16V
The capacitance value of a capacitor with a small capacity is represented by letters or numbers on the capacitor
Letter notation: 1m = 1000 uF 1P2 = 1.2PF 1n = 1000PF
Digital notation: Generally, three digits are used to represent the capacity, the first two digits represent significant digits, and the third digit is the magnification.
For example: 102 means 10 × 102PF = 1000PF 224 means 22 × 104PF = 0.22 uF
3. Error table of capacitance
Symbol FGJKLM
Allowable error ± 1% ± 2% ± 5% ± 10% ± 15% ± 20%
Such as: a ceramic capacitor of 104J indicates a capacity of 0.1 uF and an error of ± 5%.
3. Crystal diode
Crystal diodes are commonly used in circuits with "D" plus numbers, such as: D5 means the diode number 5.
1. Function: The main characteristic of the diode is unidirectional conductivity, that is, the on-resistance is very small under the action of forward voltage; while the on-resistance is extremely large or infinite under the action of reverse voltage. Because of the above characteristics, diodes are often used in cordless telephones for rectification, isolation, voltage stabilization, polarity protection, coding control, frequency modulation and noise suppression circuits. The crystal diodes used in telephones can be divided into rectifier diodes (such as 1N4004), isolation diodes (such as 1N4148), Schottky diodes (such as BAT85), light-emitting diodes, voltage regulator diodes and so on.
2. Identification method: The identification of the diode is very simple. The N pole (negative pole) of the small power diode is mostly marked with a color circle on the surface of the diode. Some diodes also use the special symbol of the diode to indicate the P pole (positive pole) or N pole (Negative), there are also signs with symbols "P", "N" to determine the polarity of the diode. The positive and negative poles of the light-emitting diode can be identified by the length of the pin, the long foot is positive, and the short foot is negative.
3. Test notes: When using a digital multimeter to measure the diode, the red test lead is connected to the anode of the diode, and the black test lead is connected to the cathode of the diode. The measured resistance value at this time is the forward conduction resistance of the diode. The connection of the multimeter leads is just the opposite.
4. Comparison of the commonly used 1N4000 series diode withstand voltage as follows:
Model 1N4001 1N4002 1N4003 1N4004 1N4005 1N4006 1N4007
Withstand voltage (V) 50 100 200 400 600 800 1000
Current (A) is 1
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