The RS232 interface is a standard interface development by the Electronics Industries Association (EIA). Communication as defined in the RS232 standard is an asynchronous serial communication method. The word serial means, that the information is sent one bit at a time. Asynchronous tells us that the information is not sent in predefined time slots. Data transfer can start at at any given time and it is the task of the receiver to detect when a message starts and ends.
RS232(Recommended standard 232) is a standard for serial binary data signal connecting between a DTE and a DCE. It is commonly used in computer serial ports. The standard as been renamed as the sponsoring organization changed it´s name and has been variously known as EIA RS 232, EIA 232, and most recently as TIA 232.
The RS232 interface expects a modem to connect to both the receiving and the transmitting end. The modem is termed as DCE(Data communication equipment) and the computer, terminal is known as DTE(Data terminal equipment).
The DCE and DTE are linked via a cable whose length should no exceed soft. The DTE has 25 pin D-type male connector and the DCE has 25 pin D-type female connector.