GB654584A - Apparatus for recording of electric impulses - Google Patents

Abstract

654,584. Magnetic sound recording and reproducing apparatus. DIAMAND, W. March 11, 1949, No. 3954/48. [Class 40 (ii)] In a magnetic recording and reproducing apparatus in which parallel curved tracks are formed on a moving magnetic strip 1 by means of a plurality of magnetic transducers 7 radially mounted and equally spaced on a revolving plate, the said transducers are so arranged during recording that one transducer is still recording at the end of one track after the next transducer has commenced at the beginning of the next track, both transducers recording at full intensity during the overlapping period. In order to obtain a smooth change-over from one track to another during reproduction, the signal current in one transducer is progressively decreased as the current in the next is progressively increased. The electric connection with the transducers may be by slip rings, and the change-over controlled by electric contacts or relays operated by the rotating disc to produce pulses causing the extinction of current in one transducer while causing the simultaneous appearance of current in the next transducer. The transfer may be effected smoothly by arranging that the said pulses control two pentode circuits, the anode current versus grid voltage characteristic of which are logarithmic, i.e. the output current proportional to the product of two input voltages, the pulse signal being of such a nature as to produce an auxiliary voltage in one circuit causing a proportional extinction of current, and in the other circuit a proportional increase of current. The plate carrying the transducers is provided with teeth 9 engaging a gear-wheel 10 on a worm shaft driving a sprocket 4 which controls the velocity of the tape past the transducers. A lever 17 and an actuating solenoid 21 is provided to enable the tape to be disengaged from the sprocket 4 to allow the tape to run at an increased speed for locating quickly a desired part of the record. The distance of this high-speed travel of the tape may be defined by arranging a reproducing head at the edge of the tape where equidistant markings have been recorded magnetically. The output current from this head may then feed an electronic counter followed by a mechanical counter. A pre-setting arrangement may be provided whereby the counters operate a relay at the pre-set marking and restore the tape to its slow movement automatically, ready to start reproducing.