Circuit diagram of switching power supply based on μA741
As shown in the figure, it is a novel design of switching power supply. This power supply uses the operational amplifier μA741 as a comparison control component, and two triodes are combined as an adjustment component, and the circuit operates in a switching state. When the output voltage is 2mV lower than the reference voltage, that is, the μA7412 pin is 2mV lower than the 3 pin (because the reaction sensitivity of the μA741 is 2mV), the μA7416 pin outputs a high level, and the control VT1 and VT2 are turned on, with a large current as a load and related filtering. Capacitors C2, C3 and other supplementary energy, quickly increase the output voltage to 12V, that is, the μA7412, 3 feet are equal. Its 6-pin output is low voltage (2V), VT1 and VT2 are turned off, and the supplementary power is suspended. As time goes on, the output voltage gradually decreases, and the above process is repeated. The power supply is continuously switched on and off, and the output voltage is always stabilized at 12V.
A communication Cable Assembly is a Wire Harness used to transmit signals. A communication cable consists of a plurality of mutually insulated wires or conductors to form a cable core, with a communication line with a sealing sheath on the outside. Some are also equipped with an outer sheath outside the sheath. There are various laying methods such as overhead, direct burial, pipeline and underwater. According to the structure, it is divided into symmetrical, coaxial and integrated cables; according to functions, it is divided into field and permanent cables (underground and submarine cables). The communication cable has a wider transmission frequency band, a larger communication capacity, and less external interference, but it is not easy to repair. It can transmit phone calls, telegrams, data and images, etc.
Communication cable assembly can be classified mainly by cable types and applications
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According to the type of cable, communication cables are classified as follows:
1. Single-conductor: refers to the most primitive communication cable, a single-conductor loop, with the earth as the regression line.
2. Symmetrical cable: a loop composed of two identical conductors under ideal conditions.
3. Coaxial cable: The inner and outer conductors on the same axis form a loop, the outer conductor surrounds the inner conductor, and the two are insulated at the same time.
Then they are classified according to the application as follows:
1. Long-distance cable: The transmission distance is long, and it is generally multiplexed. Most of them are directly buried in the ground. In a few cases, they are installed overhead or installed in pipelines.
2. Cables in the city: the wires in the cable are "paired and paired", and the number of pairs is large. Generally installed in the pipeline, a small number of urban cables are attached to the building or installed overhead.
3. Office cable: mainly refers to the communication cable used in the telecommunications office, generally installed on the distribution frame, and some are installed in the wiring trough; the office cable is used between the transmission equipment and the switching equipment in the telecommunications office, and other Inside of intra-office equipment. In order to prevent fire inside the telecommunication bureau, it is sometimes necessary to add a flame retardant sheath to the bureau cable.
