GB1385896A - Manually operable control arrangements for controlling electrical signals such as the outputs of frequency synthesizers - Google Patents

Abstract

1385896 Frequency synthesis RACAL COMMUNICATIONS Ltd 1 March 1972 [8 March 1971] 6259/71 Heading G4H [Also in Division H3] Apparatus for generating a range of frequencies, the output of which may be swept up or down through this range in steps of, e.g. 10 or 100 Hz comprises a plurality of single decade decimal counters 6C-17C connected in cascade and each adapted to supply a BCD word 6B- 17B to an associated control device 6-17 each device being arranged to control the value of one digit in the value of an output frequency produced at 18, 20, e.g. a value of 5 at 6B will cause a 50 Hz signal to be produced at 20, a value of 6 at 12B and zero at all the other inputs 6B-10B, 14B-17B will cause a value of 60 kHz to be produced at 20. Input pulses are supplied by manual rotation of a disc 54 having evenly spaced circumferential marks thereon which are arranged to interrupt a light beam impinging on two photo-cells 60, 62 via a stationary mask containing similar marks slightly skew to the first so that two approximately sinusoidal wave forms of a 90 degree phase difference are produced and fed to a detector 64 where one of these waveforms is used to generate input pulses to the counter on line 66 and where the phase difference is investigated to enable one of two AND gates 72, 74 according to the sense of rotation of the disc 54, so that the pulses reach the counter by either line 26 or 28 according as to whether the frequencies are to be scanned upwards or downwards. In operation counter 6C counts to 9 and resets to zero sending a pulse over line 22 or 24 to the counter 8C and then commences to count to 9 again, and so on. The speed of scan may be modified using AND gates 84, 85 which may be enabled by switch and line 88-92 to disable AND gates 80, 82 and thereby cause the pulses to be fed straight to the second stage 8C of the cascade. The position LOCK shown causes both sets of gates to be disabled and the output frequency to be locked at the presently occurring value. In a modification Fig. 4 (not shown) a detector is employed to detect the rate of rotation of the disc and if this is above a certain level, causes an auxiliary generator to pass additional pulses to the counter. In a second modification, Fig. 1 (not shown), a lever switch is employed, the direction of displacement of which indicates the direction of count and the magnitude of displacement being adapted to control the frequency of an input pulse generator.