Serielinjer

Serielinjer, or serial lines, are communication channels that transmit binary data one bit at a time over a single conductor or a pair of conductors. They contrast with parallel lines, where multiple bits are sent simultaneously. A serielinje may be point-to-point or part of a larger serial bus, and they are defined by standards that specify electrical characteristics, connectors, and signaling methods.

Serial communication can be asynchronous or synchronous. In asynchronous serial lines, data is framed with start and stop bits at a fixed baud rate, allowing devices to communicate without a shared timing clock. Synchronous serial lines coordinate timing with a clock signal, enabling higher throughput and more compact framing. Signaling can be single-ended, as in RS-232, or differential, as in RS-422 and RS-485, which improves noise immunity over longer distances.

Historically, serielinjer were widely used to connect terminals, printers, modems and various computer peripherals. The approach reduced wiring complexity and enabled longer link distances compared with parallel connections. In consumer devices, USB and Ethernet largely supplanted traditional RS-232 ports for many applications, but serial lines remain essential in embedded systems, industrial automation and aviation where simple, robust and low-cost links are advantageous.

Today, serielinjer are commonly implemented as UART interfaces inside microcontrollers and as physical layers for industrial protocols such as Modbus RTU or various fieldbuses. They continue to play a central role in testing, instrumentation and data acquisition, where reliable point-to-point or small-bus communication is required. Related topics include serial communication, UART, RS-232, RS-485, RS-422, and Modbus RTU.