Abstract: The RKE system allows the user to use the transmitter on the key fob to lock the car door or unlock it. In addition, the RKE also has an anti-theft function. MELEXIS wireless transceiver chip is very suitable for use in car remote control access control, it only consumes 5nA power supply current in standby mode. RKE (Remote Keyless Entry) is the abbreviation of remote access control system / remote control door switch. The RKE system allows the user to use the transmitter on the key fob to lock the car door or unlock it. The transmitter transmits data to the car and the user presses the button switch on the key fob to trigger the system to work. In addition to the technology of opening the car brakes, RKE also has an anti-theft function. It consists of a receiving controller mounted on the car and a transmitter carried by the user, ie the wireless remote control door key. The composition of the RKE system The RKE system allows the user to use the transmitter on the key fob to lock the car door or unlock it. The transmitter transmits data to the car and the user presses the button switch on the key fob to trigger the system to work. This will wake up the CPU inside the RKE key fob, and the CPU will send the data stream to the radio frequency (RF) transmitter. The data stream is typically 64 to 128 bits long and includes a preamble, a command code, and a rolling code. The data stream is typically transmitted at a rate of 2 kHz to 20 kHz. The modulation method is amplitude keying (ASK), the main purpose is to extend the battery life of the key fob. RKE key and base station structure The Melexis low-power 425MHz to 445MHz transmitter MLX72013 from Shiqiang is especially suitable for the RKE system, which is available in an 8-pin SCIC-8 package. Its 1.9V to 5.5V supply range allows the device to be powered from a single-cell Li-Ion battery and consumes only 5nA of supply current in standby mode. Block diagram of Shiqiang RF transmitter MLX72013 When transmitting Manchester encoded data, the Shiqiang MLX72103 supports data rates up to 40kbps, consumes 2.9mA and 5.5mA supply current, and delivers -10dBm to +10dBm output power to 50Ω loads. The crystal-based phase-locked loop produces an accurate carrier frequency that allows the receiver to use a narrower IF bandwidth to increase the transmission distance. For the RKE receiver, Shiqiang also offers the MLMHz7112 superheterodyne ASK receiver 315MHz to 915MHz. The MLX71121 is a highly integrated single-channel/dual-band RF receiver based on a double-conversion superheterodyne architecture. Can be used with the MLX72103. More RKE solution information or sample applications can be obtained by logging in to the Shiqiang Component E-commerce App. Shiqiang components e-commerce intelligent hardware innovation service platform provides engineers with comprehensive coverage of technical support and quality service experience. Shiqiang RF Receiver MLX71121 Block Diagram The story of Ethernet began in the ALOHA period. The exact time was after a student named Bob Metcalfe received a bachelor's degree from the Massachusetts Institute of Technology and moved to Harvard University across the river to pursue a PhD. During his studies, he came into contact with Abramson's work, and he was very interested in it. After graduating from Harvard, he decided to stay in Hawaii for vacation before going to Xerox Palo Alto Research Center to work in order to help Abramson work. When he arrived at the Palo Alto Research Center, he saw that researchers there had designed and built machines that would later be called personal computers, but these machines were solitary; he used the knowledge he gained to help Abramson work with his colleague David Boggs designed and implemented the first local area network. The local area network uses a long thick coaxial cable and runs at a rate of 3Mbps. Voip Function,Phone Port,Voip/FXS Port,Telephone Port, FXS Port Shenzhen GL-COM Technology CO.,LTD. , https://www.szglcom.com
They named this system Ethernet, and people once thought that electromagnetic radiation could be transmitted through it.
Shared medium
The Carrier Sense Multiple Access (CSMA/CD) technology with collision detection specifies a method for multiple computers to share a channel. This technology first appeared in the ALOHAnet developed by the University of Hawaii in the 1960s, which uses radio waves as a carrier. This method is simpler than token ring network or main control network. When a computer wants to send information, it switches between the following actions and states:
Start-If the line is idle, start the transmission, otherwise skip to step 4.
Send-If a conflict is detected, continue to send data until the min echo receive interval is reached to ensure that all other transponders and terminals detect the conflict, and then skip to step 4.
Successful transmission-report to the higher-level network protocol that the transmission was successful, and exit the transmission mode.
Line is busy-keep waiting until the line is free.
Line is idle-before reaching the maximum number of attempts, go to step 1 to try again at random intervals.
Exceeded the maximum number of transmission attempts-report the transmission failure to the higher layer network protocol, and exit the transmission mode.
Because all communication signals are transmitted on the shared line, even if the information is only sent to one of the terminals (destination), it will be sent to all computers on the line in the form of broadcast. Under normal circumstances, the network interface card will filter out the information that is not sent to itself, and will send an interrupt request to the CPU when it receives the information whose destination address is its own, unless the network card is in Promiscuous mode. This "one talk, everyone listen" characteristic is the security weakness of the shared medium Ethernet, because a node on the Ethernet can choose whether to listen to all the information transmitted on the line. Sharing cables also means sharing bandwidth, so in some cases the speed of Ethernet may be very slow, such as after a power failure, when all network terminals are restarted.