Clearing, in telecommunications means: A sequence of events used to disconnect a telephone call and return to the ready state for the next call setup. It is sometimes, particularly in the context of common-channel signaling, called teardown. Removal of data from an automated information system (AIS), its storage devices, and other peripheral devices with storage capacity, in such a way that the data may not be reconstructed using normal system capabilities (i.e. through the keyboard).
Note: An AIS need not be disconnected from any external network before clearing takes place. Clearing enables a product to be reused within, but not outside of, a secure facility. It does not produce a declassified product by itself, but may be the first step in the declassification process.
See also Disengagement originator National Information Systems Security Glossary
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