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When communicating at high data rates, or over long distances in real world environments, single-ended methods are often inadequate. Rather, the transmitter and receiver must be communicating using a known baud rate, or bit frequency. The specification allows for data transmission from one transmitter to one receiver at relatively slow data rates (up to 20K bits/second) and short distances (up to 50Ft. @ the maximum data rate). RS423 is another single ended specification with enhanced operation over RS232; however, it has not been widely used in the industry. Especially when the transmission is carried over a long wire outdoor, the wires is potential to carry the dangerous signal like lightning or other high voltage induction. Standards have been developed to insure compatibility between units provided by different manufacturers, and to allow for reasonable success in transferring data over specified distances and/or data rates. While the standards bring uniformity to data communications, many areas are not specifically covered and remain as "gray areas" for the user to discover (usually during installation) on his own. Each of the two UARTs on the wildcard is capable of full-duplex communications, meaning that both transmission and reception can occur simultaneously (although the RS485 protocol is half duplex as explained below).

A true multi-point network consists of multiple drivers and receivers connected on a single bus, where any node can transmit or receive data. RS485 is specified for multi-point communicates where multiples devices have their own address on the same communication line, while RS232 is only specified for point-to-point communications. While a multi-drop "type" application has many desirable advantages, RS422 devices cannot be used to construct a truly multi-point network. RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol. In its simplest form, a pair of converters from RS232 to RS422 (and back again) can be used to form an "RS232 extension cord." Data rates of up to 100K bits / second and distances up to 4000 Ft. Any number of characters can be sent, and the transmitter will automatically re-trigger with each new character (or in many cases a "bit-oriented" timing scheme is used in conjunction with network biasing for fully automatic operation, including any Baud rate and/or any communications specification, eg.

Even parity means that the bits sum to an even number, and odd parity means that the bits sum to an odd number. Parity options include even, odd, high, low, or no parity. High (mark) parity means that the parity bit is always logic 1 at the UART, and low (space) parity means that the parity bit is always logic 0 at the UART. An optional parity bit can be specified to enable error detection by the UART. No parity means that there is no parity bit. To configure a RS485 Extension you first have to choose the baud rate, parity and stop bits. Modem to phone line communications use rates of 110, 150, 300, 600, 1200, 2400, 3000, and 3200 baud. Modem to modem lines often use 1200, 4800, 9600, 14400, 28800, 33600, rs485 cable and 56000 baud. RS422 (differential) was designed for greater distances and higher Baud rates than RS232. The older RS232 standard uses single-ended signals, is more sensitive to noise, and is only rated for distances up to 50 ft (15 meters). Not more than one breakout board is required per RS485 line.

The connection between two or more elements (drivers and receivers) should be considered a transmission line if the rise and/or fall time is less than half the time for the signal to travel from the transmitter to the receiver. So long as the error between the actual baud rate and that specified is less than 1.5% (or the error between transmitter and receiver is less than 3%) there should be no communication errors. Receiver Input Resistance (Ohms), (1 Standard Load for RS485) 3k to 7k 4k min. If A is negative with respect to B, the state is binary 1. The reversed polarity (A positive with respect to B) is binary 0. The standard does not assign any logic function to the two states. The standard does not discuss cable shielding but makes some recommendations on preferred methods of interconnecting the signal reference common and equipment case grounds. Differential signals can help nullify the effects of ground shifts and induced noise signals that can appear as common mode voltages on a network. RS485 extends the common mode range for both drivers and receivers in the "tri-state" mode and with power off.