RS485 communication cable

Typical serial communication standards are RS232 and RS485, which define voltage, impedance, etc., but do not define software protocols. The characteristics different from RS232 and RS485 include:
1. Electrical characteristics of RS-485: logic "1" is represented by the voltage difference between the two lines as + (2-6) V; logic "0" is represented by the voltage difference between the two lines as - (2-6) V . The interface signal level is lower than that of RS-232-C, so it is not easy to damage the chip of the interface circuit, and the level is compatible with the TTL level, which can be easily connected with the TTL circuit.
2. The maximum data transmission rate of RS-485 is 10Mbps.
3. Strong RS-485 interface, that is, good anti-noise interference.
4. The standard value of the maximum transmission distance of the RS-485 interface is 4000 feet, which can actually reach 3000 meters (theoretical data, in actual operation, the limit distance is only about 1200 meters), and the RS-232-C interface is in the Only one transceiver is allowed to be connected to the bus, that is, single-station capability. The RS-485 interface allows up to 128 transceivers to be connected on the bus. That is, it has multi-station capability, so that users can easily establish a device network with a single RS-485 interface.
Because the RS-485 interface has good anti-noise interference, the above advantages such as long transmission distance and multi-station capability make it the preferred serial interface. Because the half-duplex network formed by the RS485 interface generally only needs two connections, the RS485 interface uses shielded twisted pair transmission. The RS485 interface connector adopts DB-9 9-pin plug socket, the RS485 interface with the intelligent terminal adopts DB-9 (hole), and the keyboard interface RS485 connected with the keyboard adopts DB-9 (pin).