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Aside from uncommon applications that use the last bit (usually the 9th) for some form of addressing or special signaling, mark or space parity is uncommon, as it adds no error detection information. However, non-standard implementations exist, for example, printers that use DTR as flow control. Flow control is used in circumstances where a transmitter might be able to send data faster than the receiver is able to process it. Central to the KNX architecture concepts are datapoints (inputs, outputs, parameters, what is control cable and diagnostic data) which represent process and control variables in the system. In particular, since many devices do not use all of the 20 signals that are defined by the standard, connectors with fewer pins are often used. Serial ports use two-level (binary) signaling, so the data rate in bits per second is equal to the symbol rate in baud. Electronic devices usually use one stop bit. The total speed includes bits for framing (stop bits, parity, etc.) and so the effective data rate is lower than the bit transmission rate. Decreasing the bit rate allows longer network distances (e.g. 500 m at 125 kbit/s).

A node may interface to devices from simple digital logic e.g. PLD, via FPGA up to an embedded computer running extensive software. ISO 11898-2:2016 specifies the high-speed (transmission rates of up to 1 Mbit/s) medium access unit (MAU), and some medium-dependent interface (MDI) features (according to ISO 8802-3), which comprise the physical layer of the controller area network. The order of bits is not usually configurable within the serial port interface but is defined by the host system. Serial computer mice may draw their operating power from the received data or control signals. Phase wire in a circuit may be any color other than green, gray, or white (whether these are solid colors or stripes). 8 data bits are almost universally used in newer applications. Most serial communications designs send the data bits within each byte least significant bit first. To cope with this, serial lines often incorporate a handshaking method.

A common commercial application of this principle was for some models of uninterruptible power supply which used the control lines to signal loss of power, low battery, and other status information. Space (S) parity always sends the parity bit in the space signal condition (0 bit value). To allow detection of messages damaged by line noise, electromechanical teleprinters were arranged to print a special character when received data contained a parity error. If slow electromechanical teleprinters are used, one-and-one half or two stop bits may be required. 7/E/1 (7E1) means that an even parity bit is added to the 7 data bits for a total of 8 bits between the start and stop bits. The total GPU memory bus width varies with the number of memory chips and the number of lanes per chip. The dominant state is transmitted by driving CANH towards the device power supply voltage (5 V or 3.3 V), and CANL towards 0 V when transmitting a dominant (0), while the termination resistors pull the bus to a recessive state with CANH at 0 V and CANL at 5 V. This allows a simpler receiver that just considers the sign of CANH−CANL. The second value is the maximum permissible effective value between two conductors of the same voltage system, i.e. L1-L2.

Signal Ground is a common return for the other connections; it appears on two pins in the Yost standard but is the same signal. 2.5 or 3.5 mm connectors and the most basic 3-wire interface-transmit, receive and ground. The DB-25 connector includes a second Protective Ground on pin 1, which is intended to be connected by each device to its own frame ground or similar. Another common connector is a 10 × 2 pin header common on motherboards and add-in cards which is usually converted via a ribbon cable to the more standard 9-pin DE-9 connector (and frequently mounted on a free slot plate or other part of the housing). The 9-pin DE-9 connector has been used by most IBM-compatible PCs since the Serial/Parallel Adapter option for the PC-AT, where the 9-pin connector allowed a serial and parallel port to fit on the same card. At least some Morse code training software used a code key connected to the serial port to simulate actual code use; the status bits of the serial port could be sampled very rapidly and at predictable times, making it possible for the software to decipher Morse code.