3. Serial bus

3.1 RS-232C/D standard (V.24/V.28)

The EIA RS-232 (Recommended Standard) was established in 1962 by the Electronic Industry Alliance. It enables interfacing between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) using serial data exchange. The revision version is designated C (established in 1969) or D (established in 1986).

The serial bus may take the form of a DB-25 male connector, but a DB-9 male connector is increasingly used, as it takes up less space. The equivalent international standard is V.24, which defines the mechanical characteristics and nature of the signals, while V.28 defines the appropriate voltages.

To increase noise immunity, characteristic voltages are used (figure