 G.721 and G.723, to allow conversion between 64 Kbps PCM and 40, 32, 24 or 16 Kbps channels. Asymmetrical Digital Subscriber Line. A method of sending high-speed data over existing copper-wire twisted pair POTS lines. ADSL, developed by Bellcore and deployed by the telephone companies, uses a modulation technique known as discrete multitone (DMT) to transmit multimegabit traffic more slowly upstream than downstream. ADSL will not work over portions of the network that attenuate signals above 4 kHz. It also can not be used where there is bridged taps and cross-coupled interference. affine map A function that identifies similar frequency patterns in an image and uses one to describe all that are similar. Advanced Intelligent Network. A digital network architecture based on out-of-band signaling that maximizes the intelligence, efficiency, and speed of the PSTN. AIN relies on databases that store vast amounts of data about network nodes and end- points and which are accessed across a packet- switched network that is separate from the one that carries customer traffic. AIN allows moment-to- moment call routing, automatic number identification (ANI), customer call-control, and more. algorithm A computational procedure that includes a prescribed set of processes for the solution of a problem in a finite number of steps; the underlying numerical or computational method behind a code or process. Algorithms are fundamental to image compression (both motion and still), because they allow an information-intensive file or transmission to be squeezed to a more economical size. Video Communication: the Whole Picture alias Unwanted signals generated during the A-to-D conversion process. Aliasing is typically caused by a sampling rate that is too low to faithfully represent the original analog signal in digital form; typically, this occurs at a sampling rate that is less than half the highest frequency to be sampled. aliasing A subjectively disturbing distortion in a video signal that manifests in different ways depending on th