Abstract: Clock and binary NRZ signals are derived from a data track of a magnetic tape. The data track includes a pattern having a substantially constant wave length of magnetic flux variations along its length. The variations are in the form of a carrier wave having only three predetermined envelope levels. One of the levels is provided for clock pulses and the other two levels are provided for the magnitudes of the binary NRZ signals. A replica of the variations is transduced by a head into an electrical signal. First and second signals are derived in response to the electric signal to respectively indicate the carrier wave having amplitudes above first and second values of the levels. The first level is greater than the level of one of the binary signals, while the second level is greater than the first level and the level of the clock pulses.

Abstract: A system for automatically supplying information to an operator, such as a student being taught to repair a piece of equipment, includes a magnetic tape storage medium having audio and video information storage tracks. A coded data signal track having indicia for locations of the information on the video and audio tracks is provided. An operator station includes keys for entering answer and command signals that control movement of the tape, so that the tape is advanced at a normal speed whereby the audio and video information is presented to the operator at a normal rate, the medium is advanced at a high speed to minimize the time that no meaningful information is presented to the operator, the medium is reversed at high speed, or stopped. Indexing of the tape can be performed by the operator selecting predetermined location indicia or in response to the operator selecting certain commands or answers in response to the audio and video information presented to the operator.