RS-232 Quick Facts
RS-232 is a point-to-point serial communications standard that defines the electrical and mechanical details of the interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE). Compared with newer standards RS-232 is limited in terms of data rate, maximum distance and noise immunity. The standard defines 25 electrical connections including data lines, control (hardware handshake) lines, timing lines and special secondary function lines. In typical applications many of these lines are not used.
Cables: When connecting a DTE to a DCE all connections are straight through. When connecting a DTE to a DTE a special ‘null modem’ or crossover cable is required.
Connectors: The original RS-232 connector was a DB-25, which supported all RS-232 lines. Often, DB-9 connectors are used, which support the most common data and hardware handshake lines.
Speed/Distance: The standard suggests RS-232 can operate at about 20 kbps over distances of 50 feet, a conservative estimate depending on grounding and noise considerations. Over short distances RS-232 is sometimes operated at rates as high as 115.2 kbps. Several hundred feet is possible at data rates of 9600 bps or lower.
Tech Tip: For longer distances, higher speeds and more noise immunity, convert to RS-422 for point-to-point, or RS-485 for multi-drop applications.
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