Method of helical scan magnetic tape recording

DETAILED DESCRIPTION In the recording method in accordance with the invention, a longitudinal track recording is used wherein the trailing edge modulation for the phase reference pulses on the synchronising track is not possible because of their large resolution requirements and the high frequency thereby entailed.
The recording method in accordance with the invention is intended to manage with one or two additional longitudinal tracks in dependence on the constructional stage.
The time code information that is to be recorded is divided into two portions.
One portion contains the relevant values such as hours/minutes/seconds (h/m/s).
This portion is recorded in a first track with a bit separation that can also be read at high tape speeds.
The second portion contains the frame count information and is either recorded in a separate track (Solution 1) or else is multiplexed into the signal of the first track by frequency division (Solution 2).
In a first inventive solution, the signal of the track 1 (hereinafter referred to as S1), as shown in FIG.
1, contains one information bit every 40 mS.
Each frame signal identifies a self-contained region of the data recorded in the helical tracks.
The frame signal is supplied to the servo system of the video signal processing means, has a time duration of 40 mS and is used for servo synchronisation.
Thus, a period of 25 frame pulses only covers the time span of one second.
The recorded signal of the first three frame pulses has a symmetrical rectangular sequence with a pulse to pause ratio of exactly 50% and is used for synchronisation.
The subsequent data bits are width modulated where a pulse/pause ratio of 25% represents an H, high or logical 1 data bit and 75% represents a L, low or logical 0 data bit.
The evaluation or decoding method for signal S1 employs counting stages which increment during the H, high or logical 1 state of the input signal and decrement during the L, low or logical 0 state.
The counter reading or value is stored for each positive edge, thereafter, the counter is reset