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The basics of RS-232

General

The RS-232 standard for serial communication was defined back in 1969 by Electronic Industries
Alliance (EIA). The idea of the RS-232 standard is to make an identical hardware interface between
two units. By now the RS-232 standard has gone through several upgrades and the interface has
been defined with greater precision and performance has been improved. The last revision of the
RS-232 was in 1997.
When using RS-232 you can make a point-to-point connection between two units. Both connected
units must know the transmission speed, number of data bits, number of stop bits and the use of
parity. If this is not the case the units will not be able to communicate.

How and why RS-232 is used

The RS-232 interface is extremely common. The RS-232 interface became popular because it is
simple and cheap. It was quickly adopted by the computer industry and was commonly referred
to as the “serial port.” The serial port could be used to connect a computer to a modem or many
other peripheral devices. It was the predecessor of the modern day USB port.
Over the last decade, use of RS-232 in the computer world has been reduced dramatically in favor
of the USB interface. But the RS-232 still offers an easy, cheap and reliable interface, and is still
commonly used in many industries. In the AV industry, the RS-232 interface is still the most com-
mon way of controlling AV-equipment such as projectors, video/audio switches and audio amplifi-
ers.

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