Serial Communications

The need to communicate between distant computers led to the use of the existing phone network for data transmission. Most phone lines were designed to transmit analogue information – voices, while the computers and their devices work in digital form – pulses. So, in order to use an analogue medium, a converter between the two systems is needed. This converter is the modem, which performs MOdulation and DEModulation of transmitted data. It accepts serial binary pulses from a device, modulates some property (amplitude, frequency, or phase) of an analogue signal in order to send the signal in an analogue medium, and performs the opposite process, enabling the analogue information to arrive as digital pulses at the computer or device on the other side of connection.

PCs have always provided the means to communicate with the outside world – via a serial communications port – but up until the 1990s, it was a facility that was little used. The ability to access bulletin boards and to communicate via fax did attract some domestic users, but in general a modem was considered as a luxury item that could be justified only by business users. The tremendous increase in the popularity of the Internet has changed all that in recent years and nowadays the ability to access the World Wide Web and to communicate via email is regarded as essential by many PC users.

PC Components | Processors (CPUs) | PC Data Storage | PC Multimedia | PC Input/Output | Communications | Mobile Computing

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