Digital signaling has evolved from early telegraphy to parallel interfaces and serial data streams. It has many possibilities for new products and services in communications and automation. Digital signal processing technology has improved the speed and quality of analog to digital conversion, allowing for clearer pictures and interactive TV.
Digital signaling is the exchange of encoded voltages or currents to effect control communications between two modules or equipment. It started with early telegraphy and very slow speed telephony. Later, digital signaling existed at parallel interfaces between equipment and later as a serial data stream. Digital signage has the potential to provide new solutions in all aspects of daily life. There are many possibilities for new products and services in both communications and automation.
Early telegraphy that began in the late 1800s was a series of dots and dashes representing encoded characters, which could be thought of as slow digital signals. Later, telephone systems used another slow on-hook/off-hook signaling and pulse dialing. By cutting off the line power, a telephone user was able to signal numbers being dialed. In the late 1900s, parallel digital signaling was very common between modules in computer equipment and accessories such as printers and hard drives. For example, transistor-transistor (TTL) logic devices were a very popular family of digital circuits that used 0 to 5 volts direct current (VDC) as the standard levels for digital signaling.
As of 2011, there were hundreds of variations of digital signaling used in computing and communications. The Open Systems Interconnection (OSI) layered architecture introduced signaling protocols embedded within other signaling protocols. Digital signal converters have taken many forms, such as converting wired internet to wireless internet service.
The digital television (TV) signal is now transmitted over the air and as a digital cable signal. Digital TVs can receive signals directly, while analog TVs can use a converter box. The digital TV signal produces a very clear picture free from any form of noise or distortion seen in analogue TV systems.
Digital signal processing technology has drastically improved the way and speed in which analog is converted to digital. The digital signal processor (DSP) uses very fast built-in analog-to-digital converters and the DSP units can be used in groups to compensate for any lack of speed. The digital signal will continue to be improved with the development of better and faster DSP units and components. In television, this not only provides a clearer picture but also allows for interactive TV and video on demand. The home viewer is able to report choices and responses to the television station, which is known as an interactive mode.
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