The cabling of the industrial communication systems (Modbus RS485) is different in some ways from the cabling used for power cabling and the electrician may experience some difficulties if he is not an expert in Modbus communication networks. The reason is that the serial RS232 protocol is, even its old, a very reliable, stable and solid communication protocol, which can easily be implemented with existing industrial equipment. Even RS485 is not commonly as popular as RS232 it is extremely useful for converters in industrial and commercial environments. The RS422 converter is used for data transmission, using balanced or differential signaling, it is mainly used in industrial and commercial environments since lots of process equipment and machinery have this protocol built-in. A RS232 - RS422 converter is a 4-wire, full-duplex, differential protocol with multi-drop capabilities and a recommended distance limit of 4000ft. ANSI/TIA/EIA-422-B is the American national standard for the RS422 protocol. Some of these converters can convert from RS232 to both RS485 and RS422 however many standard models only has one of the protocols. The serial RS232 to RS485 converter and RS232 to RS422 converter units, also called serial converters, are small electronic devices used to convert a serial RS232 signal, (for example the COM port in older computers) into either RS485 or RS422 signals.

Why use a RS232 - RS485 /RS422 converter? If there is a lot of environmental electrical noise then an optical isolated converter is preferred. Most newer consumer electronics comes with an USB, Firewire or other high-speed communication port, however a lot of industrial and commercial equipment, both old and new, is made only with a RS485 or RS422 serial communications port. The maximum number of repeaters that should be serially connected is 3. A higher number introduces excessive delays in the communication system. If you have configured all extensions you can build your system. The IDs have to be unique on the bus. If the PC is connected to the multiple Laureate instruments on an RS485 bus via an Ethernet-to-RS-485 gateway board or a USB-to-RS485 gateway board, use Laurel’s free XLOG2 datalogging software. The two jacks are wired in parallel by circuit traces on the circuit board. We connected the A and B wires to the pins on the adapter's circuit board. The central four pins remain their original RS232 functionality.

For RS232 a crossover cable is used where pin 1 is connected with pin 6 at the other connector, pin 2 with pin 5, etc. This interconnects the transmit and receive signals of both PLCs, and also the handshaking signals DTR and DSR. I tried connecting it directly to the computer either with a normal network cable or with a crossover cable but the web page doesn't open. This is a method for connecting multiple RS485 devices with each other over a two-wire network. A RS232 - RS485 converter is often used in industrial data acquisition and control applications where multiple serial devices communicate with each other through a converter. Due to loading limitations one of the best uses of a RS232 to RS422 serial converter might be in point-to-point communications, such as extending an existing RS232 line. 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.

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. If the bus is longer than a few meters then some kind of twisted pair cable is recommended. You can easily connect more devices by splitting the cable at one connector and adding another cable to it. Henceforth, we shall consider Slave devices to be measuring instruments with serial communication, rs485 cable even if the cabling is similar for all Modbus devices. The RS232 - RS422 converter is also often used in older serial devices such as older PLC's and terminal equipment. Extending a RS232 line is done by converting the RS232 signal into RS422 and then back to RS232 at the remote end. Although many applications use RS-485 signal levels, the speed, format, and protocol of the data transmission are not specified by RS-485.