| 摘要 |
1,143,424. Selective signalling. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 19 May, 1966 [22 May, 1965], No. 22255/66. Heading G4H. In a system which produces an output signal whose duration is dependent upon the difference in frequency between a measured frequency fm and a nominal frequency fn, cycles of the measured frequency are counted Z, Fig. 1, until a time base pulse occurs after a period t M from the instant that counting commenced, which causes either gates G v1 and G v2 to be opened and clock pulses of frequency ¢fp to be merged additively with the cycles of fm, or gates G R1 and G R2 to be opened and clock pulses of frequency ¢fp to be merged subtractively with the cycles of fm, in accordance with whether the count reached when the pulse t M occurred was less than (Fig. 2a), or greater than (Fig. 2b), a preset count Z s being the count which would be attained in a period t M if the measured frequency fm equalled to nominal frequency fn - and counting at the new rate of fm + ¢fp or fm - ¢fp continues until the counter is zeroized and the gates closed. A signal is present on one of leads AV and AR for the duration for which counting at the modified rate continues; this signal has a duration of when fm < fn, and a duration of when fm > fn. |
