GB1415035A - Magnetic recording and/or reproducing apparatus - Google Patents

Abstract

1415035 Controlling tape transport in video recorders SONY CORP 3 Aug 1973 [4 Aug 1972] 37039/73 Heading G5R A tape-transport control circuit 43 for a rotary-head video recorder 18 ensures that, on actuation of a control 44 at any time, the tape will start or stop in synchronism with the video signals, e.g. to permit immediate stop-motion playback, or editing without the introduction of phase-shifts, the actuation of the control 44 rendering the circuit responsive to video control signals, a predetermined one of which then causes the tape to start or stop. As shown, during recording alternate vertical sync. pulses separated 27 from the signal 10 trigger a monostable 29 to provide a series of control pulses at the frame frequency. Actuation of the control 44 to start or stop the tape sets a flip-flop 46; the next pulse from monostable 29, however, resets the flip-flop 46, which triggers a monostable 47 of adjustable time constant. The return of monostable 47 to its stable state switches a flip-flop 48 which operates a pinch-roller solenoid 24. The delay between the last pulse from the monostable 29 and operation of the pinch roller is made up of the time constant of the monostable 47 plus a mechanical delay, and the former is pre-adjusted so that the total delay is one frame period; the tape thus starts or stops synchronously with the next control pulse from monostable 29. This is achieved even when the mechanical delays on starting and stopping are not equal by a time constant control circuit 49. The control pulses are also recorded by a fixed head 35, and are compared 30 with pulses indicative of rotary head position in order to control the head motor 17 and synchronize the head rotation with the signals. During playback, the monostable 29 is triggered either by the control pulses played back by head 35 as shown; or by vertical sync. signals separated from the reproduced video signal, Fig. 6 (not shown); or by the synchronized head position control pulses, Fig. 4 (not shown). A circuit (57-59), Fig. 7 (not shown) may be included which monitors the head speed and closes a gate (56) to inhibit operation of the transport control circuit if the head speed falls below a certain level.