System for reproducing information signals on a magnetic tape which incrementally adjusts, in a plurality of steps the speed of the magnetic tape and the positioning and rotational speed of the magnetic head upon a change of mode

A system for reproducing information signals recorded on a magnetic tape in parallel adjacent tracks which extend obliquely relative to the longitudinal direction of said tape, in different modes of operation with different predetermined speeds of the magnetic tape, said system comprising a tape drive device, having a control input, for driving the magnetic tape at different speeds;

• at least one magnetic head;
• a head drive device, for rotating said magnetic head causing said magnetic head to consecutively scan said tracks;
• and a tracking servo system for causing said magnetic head to accurately scan said tracks, said tracking servo system including an electromechanical positioning device for adjusting the position of said magnetic head in a direction transverse to said tracks, a control circuit for generating a tracking signal for said electromechanical positioning device, and a variable-waveform sawtooth generator, having a control input, for generating a sawtooth waveform for said electromechanical positioning device to correct for tracking errors due to the speed of reproduction being different from the speed at which said tracks were recorded;
• said system further comprising a mode selection device with which an operator may select any of said modes of operation, and a switching device coupled to said mode selection device for applying, respectively, a first control signal (TW) to the control input of said tape drive device for controlling the speed of said magnetic tape, and a second control signal (DS) to the control input of said variable-waveform generator for controlling the amplitude and frequency of said sawtooth waveform, said first and second control signals being co-related so that at any speed of the magnetic tape corresponding to a particular value of said first control signal, a respective particular value of said second control signal adjusts said tracking servo system to cause said magnetic head to accurately scan said tracks, said switching device generating different respective values of said first and second control signals depending upon which of said modes is selected by the operator;
• characterized in that said switching device comprises a stepping signal generator activated by a change from a first mode to a second mode in said mode selection device, said stepping signal generator causing at least said first and second control signals to change incrementally, in a plurality of respective steps, from respective first values, corresponding to said first mode, to respective second values, corresponding to said second mode, said incremental changing of said first and second control signals being synchronous and said steps being respectively sized to maintain said co-relationship between said first and second control signals, whereby upon initiation of a mode change in said mode selection device, each incremental change in said first and second control signals does not exceed the dynamic responses of said tape drive device and said tracking servo system so that the quality of a picture on display is not degraded during a change from one mode of operation to another mode.