| 摘要 |
879,475. Electric selective signalling systems. DECCA RECORD CO. Ltd. July 29, 1960 [Aug. 4, 1959], No. 26540/59. Class 40 (1). A system for generating data representative of the angular position of a rotating body comprises means for generating main position marker pulses at a series of equally spaced angular intervals of rotation of the body to indicate when the body passes through each of these positions, means for generating identification pulses between the marker pulses to distinguish and identify the various main marker pulses and means for generating separate fractional indicating pulses between the main marker pulses to mark when the body passes through each angular position corresponding to a predetermined sub-division of the angular interval between the positions at which the main marker pulses are generated. As described two photo-electrically sensed discs 13, 14, Fig. 1, on a shaft 12 are used, one disc 13 produces regularly occurring main marker pulses 20, Fig. 2 (a) and the other disc 14 regularly occuring fractional indicating pulses 23, Fig. 2 (b) except that at the time when a main marker pulse occurs no fractional pulse occurs. As shown there are thirteen fractional pulses between each pair of main marker pulses and by counting both the main marker pulses and the fractional pulses the position of the shaft 12 could be determined. To avoid the necessity of counting the main marker pulses however, each is preceded by identification pulses 21, Fig. 2 (a) which identify, or label, it, and as described, these occur and are significant in combination, during the period occupied by the first eight fractional pulses after the preceding main marker pulse. Thus the eight fractional pulses which occur after each main marker pulse function as clock-pulses for interpreting the identification pulses. During the period between main marker pulses which is not occupied by identification pulses, other data such as pulses 24 can be transmitted. As shown in Fig. 1, the pulses from the two discs are applied to two tone generators 30, 31 and subsequently transmitted, either by radio or land line, to a receiver where the identification pulses are decoded by a device 36 and the fractional pulses are counted by a device 37, the counter being reset by each main marker pulse. |
