Graph Sequence Visualisation and its Application to Computer Network Monitoring and Abnormal Event Detection

In an apparatus for reproducing video signals recorded in successive parallel tracks extending obliquely on a record tape, which apparatus includes a rotary head repeatedly scanning across the tape generally in a direction along the tracks for reproducing the signals recorded therein while the tape is advanced longitudinally at a selected speed for achieving a desired reproducing mode, and a head deflecting device, such as, a bi-morph leaf, responsive to a drive voltage for deflecting the head in a direction transverse to said direction along the tracks; a tracking control system is provided with a circuit for detecting a deviation of the reproducing tape speed from a normal speed, preferably by detecting a frequency deviation of a sync signal included in the signals reproduced by the rotary head when scanning one of the tracks, and providing a first digital output in correspondence thereto, a circuit for detecting a phase deviation of a sync signal included in the reproduced signals, for example, the reproduced vertical sync signals, in respect to a reference sync signal and providing a second digital output in correspondence thereto, adders digitally adding the first and second digital outputs for providing an added output comprised of a plurality of bits, and a decoder responsive to only the upper bits of such added output for providing therefrom a signal which is applied to the head deflecting device as part of said drive voltage for determining the next track to be scanned by the rotary head.