Patent GB-907080-A (GB)
Title: Colour television signal reproducing system
IPC: H04N9/87
Filed: 1960-06-09
Abstract: 907,080. Television. AMPEX CORPORATION. June 9, 1960 [July 8, 1959], No. 20358/60 Class 40(3). The synchronizing signals in a composite video signal derived from a magnetic tape recording are removed and utilized to control the re-insertion of " new " synchronizing signals and, should one of the new vertical synchronizing signals be missed out due to the effect of transients, an additional source of such signals is automatically gated in. When the derived signal is a composite colour video signal of the N.T.S.C. type the sub-carrier and the " burst " signals are replaced by signals from a crystal controlled source. If, however, the derived signal is a monochrome one the absence of the colour burst is arranged to disable all the colour circuitry. As shown in Fig. 1, the video signals, recorded on and reproduced in known manner from a magnetic tape 11, are supplied via switch 81 (shown in the position for colour signal reproduction) to circuits 72, 73, the former supplying a regenerated sub-carrier controlled by the " bursts " in the input signal to circuit 73 to de-code the input video signals and supply output colour signals of the N.T.S.C. type in the form of Y, I and Q components. These latter signals are then supplied to a circuit 74 in which a new sub-carrier from a crystal controlled source 56 (which, in known manner, also controls the rotation of the reproducing heads 16) is added, thus forming a new composite video signal. The latter signals are supplied to a circuit 77 which removes all synchronizing signals and utilizes the separated signals to control the introduction of new synchronizing information, the new vertical and horizontal synchronizing signals being generated in circuit 77 and the new colour " burst " signals derived from the crystal controlled sub-carrier generator 56 via a circuit 79 controlled by a gate circuit 78 in accordance with signals separated out from the input signals to 77. The new " clean " composite video signal free from noise and errors inherent in the reproduction process is then available at the output of 77. When the signals derived from the tape relate to a monochrome television signal the circuit 72 reacts to the absence of the colour " burst " and supplies a control signal which opens the switches 81 . . . 84 to disconnect the colour circuitry. The latter includes a device 71 which introduces a delay of slightly less than one line period in input line blanking pulses so that a blanking circuit 68, which controls the commutation of the output of the rotating heads 16 in circuit 66, operates during the front porch and not during the back porch which would blank out the synchronizing colour " bursts " during colour signal operation. The output of circuit 77 is also utilized to derive, in an automatic compensation sensor device 811, an error signal (due to tape wear, expansion, &c.) which is employed, via amplifier 821, to control means 831 serving to control the pressure between the heads 16 and the tape 11. Details of 71 and 72 are given in block and circuit diagram form with reference to Figs. 2 and 3 (not shown) and of device 77, in block diagram form, with reference to Fig. 4 (not shown). Specification 859,058 is referred to.