| 摘要 |
<p>1,047,534. Electronic counters. STANDARD TELEPHONES & CABLES Ltd. May 21, 1965 [May 25, 1964], No. 21564/64. Heading G4A. The frequency of a pulse source is measured by counting the number of pulses from the source 26 until it has exceeded the capacity of a chain 28, the subsequent attainment of a point B, C or D in a timing chain 21 controlling the position of the decimal point 31 in a display 30. Initially bi-stable 23 is at 1 and all other bistables at 0. A Mc. standard frequency source 22 feeds timing chain 21. After 100 Ásecs. a pulse at A reverses count control bi-stable 20 so that the source 26 feeds its pulses to chain 28. After a further 99 periods of 100 Ásecs. B pulses transient OR gate 36 and if a pulse has passed to stage E in chain 28 then count rate sensing bi-stable 23 restores so cutting off NAND gate 25 so that the count at 28 is stopped. The count is displayed on neon tubes at 30 or may be printed. Bi-stable 20 at the end of a count controls mono-stables M to cut off the supply from the standard frequency source 20 for several seconds while the display is viewed and then to restore the circuit to original condition. If a pulse has not entered stage E when the timing chain reaches B then the process continues until a further point C or D is reached with adjustment of the decimal point position 31. If the timing chain reaches D then bi-stable 23 is reversed irrespective of whether a pulse has entered E or not. If the frequency to be measured is excessively high then stage 39 operates to energize an alarm W.</p> |
