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SC, G or reference, the common signal reference ground used by the receiver to measure the A and B voltages. RS232 referenced ground to decipher the data it was transmitting. It also defines three generator interface points (signal lines); A, B and C. The data is transmitted on A and B. C is a ground reference. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive. The two values provide a sufficient margin for a reliable data transmission even under severe signal degradation across the cable and connectors. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. Failure to stay within this range will result in, at best, signal corruption, and, at worst, damage to connected devices.

What made it such an advancement over RS232 was the fact that it could transmit not only a single device to device transmission, but also a communications bus to connect multiple devices at once. It does not specify or recommend any communications protocol; Other standards define the protocols for communication over an RS-485 link. The EIA once labeled all its standards with the prefix "RS" (Recommended Standard), but the EIA-TIA officially replaced "RS" with "EIA/TIA" to help identify the origin of its standards. Alarm systems: Rs485 cables in alarm systems help transfer alarm signals and information from alarm devices to the control center. This ensures that all security-related information and incidents are transmitted quickly and with high reliability. Cable jacket: Made from high-quality PVC, the outermost jacket layer has high elasticity, helping to protect the cable from strong environmental impacts. Control and monitoring systems: A single pair of rs485 signal cable can connect up to 32 devices, with a signal transmission distance of up to 1200m. Therefore, using rs485 cables is an ideal choice for industrial control and monitoring systems, especially those with large-scale and high dispersion. Industrial automation systems: In the industrial automation sector, rs485 signal cables play a vital role in connecting and remotely controlling motors.

All in all, RS485 really allowed full automation possible with its ability to connect so many devices at once. In order to avoid errors when many devices are connected, cables of the same colour should be used for all the connections to the terminals A and cables of the same colour should be used for all the connections to the terminals B of the various devices (e.g. white for A and blue for B). Because a mark (logic 1) condition is traditionally represented (e.g. in RS-232) with a negative voltage and space (logic 0) represented with a positive one, A may be considered the non-inverting signal and B as inverting. However this contradicts the facts that an idle mark state is a logical one and the termination polarization puts B at a higher voltage in Profibus guidelines. This helps to minimize the impact of electromagnetic interference, causing the voltage between the two wires to deviate. Each device has a communication port with two terminals, which are indicated for the sake of convenience as A and B. In these two terminals the communication cable is connected so that all the devices that take part in the communication are connected in parallel.

Unlike what happens in many energy distribution systems, the manner in which the devices are connected in parallel is important. Another advantage over RS232 that I mentioned earlier is the number of connectable devices. Using a repeater, the main cable is divided into different segments, each of which can be up to 700 m in length and connect 32 devices (this number includes the repeaters). Rs485 cables not only vary in the structure of the core but also in the number of twisted pairs. Anti-inteference layer: Rs485 cables are designed with 2 anti-inteference layers to shield the internal conductors. Rs485 cable is essentially a signal cable with a twisted pair structure, additionally shielded with 2 layers of noise protection used in industrial communication. This ensures maximum protection for the inner core. The maximum RS485 cable length is typically listed as 1200 meters or about 4000 feet. The branches must be no longer than 1200 m! Users can utilize a longer cable, up to 1200 meters or 4000 feet. These distances I'm talking about are greater than 100 meters. Digital communications networks implementing the standard can be used effectively over long distances and in electrically noisy environments. RS-485 supports inexpensive local networks and multidrop communications links, using the same differential signaling over twisted pair as RS-422.