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GSM/GPRS and RS485 LED Signs Board

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  LED Signs is widely used in square, Commercial Street, railway station, Subway, shopping malls and other places. Because of the diversity and complexity of its use, it also puts forward higher demand for the stability, reliability and fluency of audio and video signal transmission. Single-screen broadcast or networking of the LED Signs screen signal using a variety of transmission methods.The common LED Signs signal is divided into wire transmission cable signals, GPRS, 3G, 4G and other wireless signals.

  First,The classification of LED Signs signal transmission

  1, Wireless transmission: The primary reliance on wireless signal operation frequency of different classification, such as long wavelength, medium wave, shortwave, microwave and so on. Mobile phone signal is a kind of wireless access method, today a lot of mobile phone GSM operating frequency in 900MHz.There are many varieties of TV signal, such as cable TV: The general transmission of analog signals, digital television is the transmission of digital signals, satellite television signals are digital signal LED Signs signal.

  2, Wired transmission: Can be divided into analog signal transmission, digital electrical signal transmission, digital optical signal transmission.

  Second, LED Signs large signal transmission project

  In addition to the attenuation of the signal, another element that affects signal transmission is signal reflection. Impedance mismatch and impedance mismatch are the two leading reasons for the RS-485 bus to form the signal reflection. Impedance mismatch, impedance mismatch is the first 485 chip and communication lines between the impedance mismatch.

  The reason for reflection is that when the communication line is idle, all communication line signals are at sixes and sevens, once this kind of reflection signal triggers the 485-chip input-side contrast device, the fault signal will occur. The usual solution is to add a and B lines of the RS-485 bus with the offset resistor of a certain resistance, and then pull up and pull low, so as to prevent unpredictable clutter signals. Impedance is not consecutive, is similar to the light from a medium into another medium caused by the reflection. The signal is at the end of the transmission line. The cable impedance is very small and the signal will cause reflection in this locality.

  The most common way to eliminate this reflection is to cross a terminal resistor of the same size as the cable's characteristic impedance at the end of the cable.

  Third,How to ensure the security function of LED Signs signal transmission process

  China led signs manufacturer can develop a simple and reliable RS-485 communication protocol, when the communication interval is short, the use of environmental interference hours, one-way communication can complete the project function, but most of the use of the environment is not the ideal. Therefore, it is particularly important to draw up a perfect communication protocol. The specific method, the data packet transmission, after each packet data plus frame head and frame end of the method of packaging data, in which the end of the frame left a byte as a check byte. The next machine after the check byte of their own accounting and the host computer transmission over the check byte for comparison, so that the host computer to announce the instructions, in the end is sent from the packet data is still to send a packet of data, so that a package after the hair and then send the next packet, until the end of the

  After such a calibration mechanism, we can reduce the probability of error, so that the communication system to operate normally. In short, the signal in the transmission process, followed by the increase in spacing and weakened. Therefore, in order to ensure the performance of the LED Signs, display the LED Signs relative to other advertising methods, LED Signs transmission media selection is particularly important.

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