Patent GB-854651-A (GB)
Title: Improvements in and relating to the recording of television programmes
Inventor: AXON PETER ERIC
IPC: G11B27/30
Filed: 1957-09-17
Abstract: 854,651. Magnetic sound recording and reproducing apparatus. BRITISH BROADCASTING CORPORATION. Sept. 5, 1958 [Sept. 17, 1957], No. 29301/57. Class 40 (2). [Also in Group XL (b)] In an arrangement for " marking " at a desired position, a magnetic record on which television and accompanying sound signals are recorded to facilitate subsequent editing of the recording, a signal comprising an oscillation of frequency outside the frequency band of the sound signals is recorded on the sound track at the desired position under the control of an operator as the recording (magnetic tape) is " played-back " at the normal recording speed, so that, on a subsequent " run," in either direction, at a speed much lower than the recording- speed, the " marking " signal is reproduced as an audible signal free from the recorded accompanying sound signals. The sound head employed for the latter signals may be utilized for the " marking " signals or a separate head may be employed. In the described embodiment in which the latter arrangement is employed the head 39 for the marking signals, is positioned over the same track on the tape 19 as the head 14 for the accompanying sound signals, the television signals being recorded and reproduced by heads 15, 16 of which the former deals with the H.F. components in the form of amplitudevarying signals and the latter with the L.F. components in the form of frequency modulation of an oscillator produced by generator 26. With all switches in the positions shown the apparatus is conditioned for the recording of television signals from source 10 and accompanying sound signals from source 28, the tape 19 being driven by motor 18 at a speed of about 200 inches per second. When such a recording has been made and the tape rewound the positions of the (ganged) switches 13, 27, 31, 32 are reversed and on running the tape through at the same speed (200 inches per second) the recorded television signals are reproduced on a monitor tube 36 and the sound signals reproduced by a loud-speaker 35. During such monitoring run, when it is desired to identify particular portions of the tape for subsequent editing, the operator momentarily presses a key 40 which supplies to head 39 a 30 kc/s. oscillation from generator 41 which is amplitude-modulated in 42 by the frame synchronizing pulses of the system or, if desired, by spoken instructions via a microphone 46. When all the required " markings " have been effected the ganged switches are returned to the positions shown, a speed control switch 21 is put in the reverse position to that shown and (unless the tape has been rewound) a motor reversing switch 24 is also changed over from the position shown so that on pressing a switch 23 the tape is driven past the heads at a (reduced) speed of about 20 inches per second. In this condition the 30 kc/s. " marking " signal is reproduced by head 39 as a 3 kc/s. signal and this signal is fed via an amplifier 45 (which rejects the sound signals recorded by head 14 since such signals consist of a frequencymodulated 250 kc/s. carrier from generator 30) to the audio amplifier 34 and loud-speaker 35. The various editing requirements such as selective erasure, cutting and splicing of the tape may then be effected at the positions " marked," the presence of the frame pulse modulation of the " marking " signals allowing such splicing to be effected during the frame blanking periods to avoid interruptions of the frame synchronizing signals in subsequent reproductions of the recorded pictures. The precise positions of the frame pulse modulation signals may be determined by employing a " flux-sensitive " head of the kind described in Specification 782,572.