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. If you ever wanted to connect to device in the same building (e.g. to machinery on production hal) and to you have to go to it to connect your computer. In addition to the ease of integration, minimum requirement of processing power and reliability of the connectors further helps to favor these serial over Ethernet communications.A device server is used to control the whole setup via a networking technology. On the other side we also have converter RS232 - RS485 ATC - 108N, via the RS232 port is connected to cash or other device with RS232 port. Computer is connected to the converter rs232 rs422 ATC - 105. Converter is also connected to external power, supporting RS485 port. 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. RS-485 is used in basically connecting the temp sensor or thermostat in the room to the master controller.

RS-485 is used for low-speed data communications in commercial aircraft cabins' vehicle bus. Multiple receivers may be connected to such a network in a linear, multidrop bus. This allows RS-485 to implement linear bus topologies using only two wires. In theatre and performance venues, RS-485 networks are used to control lighting and other systems using the DMX512 protocol. RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. The EIA has officially disbanded and the standard is now maintained by the TIA as TIA-485, but engineers and applications guides continue to use the RS-485 designation. In contrast to RS-422, which has a driver circuit which cannot be switched off, rs485 cable RS-485 drivers use three-state logic allowing individual transmitters to be deactivated. RS-485 signals are used in a wide range of computer and automation systems. It may be used to control video surveillance systems or to interconnect security control panels and devices such as access control card readers. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement industrial control systems, including the most common versions of Modbus and Profibus.

Some of the typical applications of RS-485 is point of sale equipment. By default, all 720 series key pads come with a standard set of commands which can be used to integrate with existing applications or used to build the metal keypad into new application developments. One of the key advantages also is that RS-485 can drive data a long distance. RS-485 serves as a physical layer for the AES3 digital audio interconnect. RS-485 only specifies the electrical characteristics of the generator and the receiver: the physical layer. The fastest RS-485 transceivers out there right now are running about 50 megabits. And RS - 2322 right now, the fastest transceivers right now are 1 megabit. Plus a lot of times the data rates are so slow on these bar code readers because they're only sending a few kilobits. You probably have used this many times at stores without realizing it. So you can have a reliable, low-cost solution to a heating, ventilation control unit. DH 485 is a proprietary communications protocol used by Allen-Bradley in their line of industrial control units.

It is also used in Digital Command Control (DCC) for model railways. Because of the differential signal, any noise is subjected externally to the cable is basically subjected to both cables. Line A voltage, implying A, the green wire, is indeed connected to the driver inverting signal, as seen in a whitepaper. The diagram below shows potentials of the A (blue) and B (red) pins of an RS-485 line during transmission of one byte (0xD3, least significant bit first) of data using an asynchronous start-stop method. The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, i.e. a line or bus, not a star, ring, or multiply connected network. Ideally, the two ends of the cable will have a termination resistor connected across the two wires. RS-485, like RS-422, can be made full-duplex by using four wires. Care must be taken when using A/B naming. By using repeaters very large RS-485 networks can be formed. 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.