Modbus/TCP was introduced for LAN installations but Modbus over traditional serial transmission networks is still found in many industrial applications and building automation systems. There is also the GSM version; especially useful when only one sensor is needed in a remote location where other types of transmission cannot be used. RS-232 defines thirteen "standard" interface types lettered A through M. None of these match IBM's implementation of its serial port. One circuit (Signal Common) is required for all interface types. RS-232 allows for both a transmit and receive circuit. This kind of integration allows for one system to control many different elements within an area. The RS-232 standard includes secondary serial data circuits (secondary TX data, and secondary RX data), three clocks (timing elements) for synchronous serial data transfer, Signal Quality Detector, and more. RS-232 provides a list of circuits and says if you use a circuit; this is what it must do and it must be on this pin of the connector.

Another example of misunderstanding the RS-232 standard is the 9-pin connector. This serial port was no longer a "RS-232 compatible" serial port since the connector and signal levels no longer matched the RS-232 standard. The original "RS-232 compatible" serial port used a UART to drive the RS-232 electrical signal levels and many came to believe that the UART protocol was a part of the RS-232 standard. In RS485 mode, RS485 standard the RS422 transmit and receive pairs are shorted together with a pair of onboard jumpers as explained in the UART Wildcard Hardware: RS485 Jumpers section below. The standard RS232 to RS485 converter. Even RS485 is not commonly as popular as RS232 it is extremely useful for converters in industrial and commercial environments. This gateway has advanced features enabling it to receive custom RS232 data strings that can trigger a task or send a Dynet message on the RS485 port. The RS-485 standard calls for a differential signaling scheme that will operate over a much longer line length than RS-232 can. RS-485 does not define a communication protocol; merely an electrical interface.

These IR transmissions can be triggered from any Philips Dynalite user interface such as a pushbutton panel or even a motion sensor. When two pair of wires are used for full-duplex communications, one pair is used for the interface generator (driver) to talk to the other device(s) on the RS-422 network, and the second pair is the interface receiver used to listen to an other device (not devices, since only one driver can be on this pair of wires) on the network. Half-duplex RS-232 implementations exist but require all of the hardware and wires that a full-duplex network requires. Clearly not all of these circuits or signals are included in IBM’s implementation (very few implementations use secondary data lines or many of the other circuits). The RS-232 standard defines a DB-25 and a 26-pin alternate connector, the function of each of the pins in the connector (called circuits), and the electrical characteristics of the signals that are on the "circuits". For example, one of the circuits is "AB".

Typically one device (node) is addressed by the host computer and a response is received from that device. A circuit is a full definition of a signal from the transmitting device to the receiving device, but many now think of these definitions as pin labels. RS-485 voltages are referenced differentially from one wire to the other, but are also referenced to circuit common. Articles, application notes, even data sheets from semiconductor manufacturers discuss both the data rate and line length limits in RS-485. The RS-232 standard does not include a line length limit, but practical limits of the electrical signal levels prevent long lengths. Many think the RS-232 standard completely defines the IBM PC serial port, but this is incorrect. This defines all 25 pins of the connector. RS-232 specifies two connectors, a 25-pin (DB-25) and an alternate 26-pin connector (pin 26 is "No Connection"). Half-Duplex RS-232 is usually limited by an additional communications device between the two farthest ends that are communicating. For example; Two computers communicating with each other over an older modem. RS-232 only defines connecting DTE to DCE, so when two computers are connected together this is outside of the standard.