The term 'Digital Call Quality' had entered into popular english language in the late 20th century at a time of increasing popularity of GSM mobile (cell) phones ('2G') replacing the preceding analogue system. The popular meaning of the phrase is taken to suggest GSM audio performance is comparable to that of digital audio (such as Philips Audio Compact Disc). However, the difference here is the GSM system has been optimised to use only the minimum bandwidth required to sufficiently recreate the sound of the caller's voice enough to be recogniseable to the callee, and to recreate most the sounds that the spoken words make, sufficiently for spoken sentences to be understandable. Not to be confused with Get Some Mates The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. ... Advanced Mobile Phone System (AMPS) is the analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1984. ... The Compact Disc logo was inspired by that of the previous Compact Cassette. ... This is a list of device bandwidths: the channel capacity (or, more informally, bandwidth) of some computer devices employing methods of data transport is listed by bit/s, kilobit/s (kbit/s), megabit/s (Mbit/s), or gigabit/s (Gbit/s) as appropriate and also MB/s or megabytes per...

It must be noted that generally, that digital call quality (i.e. GSM encoding) sometimes fails to communicate certain tonal information within the voice used in human communication beyond the spoken word. (This is present in an analog channel). These include the physiologically-influenced modifications of the human voice due to the act of lying and other emotional effects affecting such things as rapid pitch delta of the voice. There are also some spoken languages and dialects which are affected more by GSM encoding than others, especially where such tongues rely on the communication of information that GSM encoding can miss. Additionally, because the duplex audio link each contains a significant time delay each direction, means conversations are not 'live'. It has been suggested that this article or section be merged into Tone (linguistics). ... An analog or analogue signal is any continuously variable signal. ...

(Note that although the previous analogue mobile phone system utilised a wider bandwidth, it operated on the simpler principle of faithfully conveying analogous 'voice-shaped' signals in real time between the calling parties, permitting additional audible communication to take place between individuals by using other than just the spoken word and missed by digital call quality). An operation within a larger dynamic system is called a real-time operation if the combined reaction- and operation-time of a task is shorter than the maximum delay that is allowed, in view of circumstances outside the operation. ...