Accounting management. Area of network management functions that deal with the identification of costs for the use of hardware and software resources.
Accuracy of a clock. The maximum time or frequency error, which may be measured in general over the whole clock life unless differently specified. The time accuracy means how well a clock agrees with UTC, while the frequency accuracy is the maximum frequency error Δvmax compared to the nominal value vn.
Add-Drop Multiplexer. Multiplexer equipment with drop and insert capability. ADMs of level N (ADMs-N) are used in intermediate nodes of SDH transmission chains or rings to insert or drop tributaries from the STM-N line in transit. Tributaries may be PDH signals of any kind and hierarchical level as well as SDH STM-M signals (M ≤ N).
Administrative Unit. SDH multiplexing element. An AU consists of a higher order VC-i (i = 3, 4) and of an AU pointer indicating the offset of the pointed VC within the AU itself.
Administrative Unit Group. SDH multiplexing element. The purpose of AUGs is similar to that of TUGs. They contain an homogeneous group of AU-3 byte-interleaved or one AU-4, located in fixed positions.
Analogue signal. A signal a characteristic quantity of which follows continuously the variations of another physical quantity representing information.
Anisochronous. A non-isochronous digital signal.
Annual wander. Wander caused by pseudo-periodical (seasonal) temperature variations on the transmission medium along ...