GB688816A - System for analysing electric signals recorded magnetically on a wire or tape - Google Patents

Abstract

688,816. Magnetic recording and reproducing apparatus. WEIBULL, E. H. W. Oct. 1, 1951 [Oct. 25, 1950], No. 22827/51. Class 40 (ii) [Also in Groups XXXVI and XL(b)] Apparatus for analysing electric signals previously recorded magnetically on a wire or tape which is movable from one magazine to another to traverse a magnetic head whose output passes through a frequency-selective filter to a cathode ray oscillograph display, comprises an electromechanical device whereby a selected length of the wire or tape is caused to perform a repeated periodic movement relatively to the head, whose output is displayed on the C.R. oscillograph against an expanded synchronized timebase. Fig. 1 shows a wire tape 6 on which signals to be examined are magnetically recorded, traversible by rotary bobbins 8, 9 round the periphery of a drum 4 carrying a magnetic head 7 whose airgap embraces the wire and whose output is connected through slip rings to a frequency-selective filteramplifier 20 feeding the Y plates of a cathode ray tube 23. As the wire is traversed, the signals selected from the recording deflect the C.R.T. trace in the Y direction until an indication of interest is displayed when the traverse is stopped and the variable speed motor 1 is started to drive the shaft 3 and rotate the drum and the magnetic head round the encircling portion of stationary wire. Simultaneously a circular resistance element 33 energized through further slip rings from a voltage source E is rotated by the drive shaft past a contact 27 which picks off a sawtooth timebase voltage energizing the X plates of the C.R.T. to repetitively display the signals recorded on the selected length of wire against an expanded synchronized timebase. The repetition speed is variable by the motor control knob 2 and the position of the trace is adjustable by a knob and pointer 31 rotating through a worm drive the loose disc 34 carrying the brush 27. In a modification Fig. 2 (not shown) the selective filter-amplifier is embodied in a commercial cathode-ray oscilloscope having an internal timebase synchronized by impulses derived from a brush rotated by the driving shaft to periodically engage a contact on the periphery of a loose disc, which is manually rotatable to adjust the trace position. Fig. 3 shows a further modification wherein motor 1 rotates the bobbins 8, 9 by bevel gears driven from a mechanical control unit 55 such that the speed and direction of rotation is adjustable by a knob 56. and when an indication of interest is displayed the drive is adjustable by knob 57 to oscillate a section of the wire encircling the drum 4 backwards and forwards past the magnetic head, which remains stationary. The circular resistance element generating the repetitive sawtooth timebase is rotated from the bobbin drive through a variable speed transmission unit controlled by a knob 69. The record wire may be looped to completely encircle the drum.