In order to appreciate the benefits of digital communication, it’s necessary to understand how it differs from analog. Put simply, older telephones communicated via analog signals which were a direct representation of the human voice. These signals are voltages that vary with frequency and volume. Telephones were connected through wires, switches, and amplifiers.
Microcircuits called digital-to-analog converters change analog signals to digital thousands of times per second. Wikipedia has a detailed discussion of how they work. These circuits measure the analog voltage at specified intervals, and produce a binary number representing that voltage. The binary number can be sent to a computer that attaches an address label for further handling. This is a digital “word.” If the interval is every ten-thousandth of a second, the computer can perform other operations while it waits for the next digital word because the computer performs millions of tasks each second. For the telephone example, this means that hundreds of individually addressed binary numbers can share a wired connection, a fiber optic cable, or a radio link.
When the same techniques are applied to television signals, more broadcasts can fit into the bandwidth defined by radio frequencies, fiber optics, or coaxial cable. These digital words include an address, data, and a checksum that indicates whether the word arrives intact and error free. This reduces the effect of electrical noise in radio communications or transmission lines.
Machines communicate via digital words. Modern automobiles and aircraft use control systems that offer both high speed and precision. Automotive engine management computers, for example, monitor an oxygen sensor in the exhaust gas and alter the air to fuel ratio thousands of times per second to enhance combustion and reduce emissions. Likewise, aircraft systems use the speed of digital communications to monitor and control thousands of critical flight parameters.
Computers use digital communications both internally and externally. Like the telephone, they convert digital to analog for audio and video use, but they also communicate directly with other devices with digital words. Internet communication utilizes packets of addressed binary numbers, while a local printer connected to the computer with a cable uses shorter binary words that represent alphanumeric characters and control codes.
Digital communications allow more users to share a finite communication resource like a cellular phone tower or a telephone line, and they allow machines to operate faster with a greater level of precision and safety.