Patent GB-869686-A (GB)
Title: Improvements in or relating to electric pulse frequency dividers
Inventor: BREWSTER ARTHUR EDWARD
IPC: H03K25/00
Filed: 1959-03-06
Abstract: 869,686. Circuits employing bi-stable magnetic elements. STANDARD TELEPHONES & CABLES Ltd. March 6, 1959, No. 7857/59. Class 40 (9). [Also in Group XIX] A frequency-divider stage comprises two similar cores of squareloop ferro-magnetic material, means for applying to driving windings on both cores a train of alternately positive and negative pulses so that the cores are subjected alternately to a change of flux, and means for deriving an output pulse in response to the next driving pulse which follows after one of the cores has reached saturation in one specified direction. Figs. 2A, 2B show the hysteresis curves of cores 1A, 1B in Fig. 1 in a system for dividing by ten. A source 12 supplies a square wave-form 12 to a driving core 2 which is thereby saturated alternately in opposite directions and supplies driving pulses alternately in opposite directions to windings 4A, 4B respectively forwardly and reversely wound on cores 1A, 1B The " ladle and bucket " ratio is 1: 5 and the cores 1A, 1B are subjected to a bias field by cores 5A, 5B, 6A, 6B, positive or negative according to the state of flip-flop 19. The flux of cores 1A, 1B is changed by forward and reverse driving pulses, respectively, until both cores are saturated, i.e. at points a5, b5 in Figs. 2A, 2B, when flip-flop 19 switches to reverse the saturation of an output core 3, 98 so producing an output pulse across terminals 15, 16. The process then continues with the functions of the driving pulses interchanged until the cores are saturated in the opposite sense when flip-flop 19 restores and an oppositely directed output pulse appears across terminals 15, 16. The terminals 15, 16 may be connected to a further dividing stage. The system described above may be modified to count an odd number such as 9, the flip-flop 19 having a sensitivity such that it responds to a whole quantum of flux change but not to a half-quantum. Frequency-division by 30. By choosing cores such as 23A, 1A, 24A with hysteresis curves of varied widths as shown in Fig. 5, it is possible to have three pairs of cores, arranged as shown in Fig. 4, to provide a frequency-division of 30. The extra pairs of cores have auxiliary bias windings 25A, 25B forwardly wound and 26A, 26B reversely wound. The first five forward pulses affect cores 23 only, the next five cores 1 only, and the third five cores 24 only and similarly for emptying the "bucket." Fig. 6 shows a separate core 28 used for controlling flip-flop 19 in a system for counting or dividing by 11. If this core is similar to 1A and 1B then winding 29 has fewer turns than 4A and 4B. When core 1A has been completely saturated by five forward driving pulses the next forward pulse cannot affect 1A but saturates core 28 to reverse flip-flop 19. Core 1B then stays one step behind 1A until the 11th forward pulse saturates 1B and the 11th reverse pulse restores 28 and flip-flop 19. Fig. 8 shows a system for distributing pulses over terminals 101-120 in that order in a 20- channel time-division communication system. The five pairs of counting cores 41A-45A, 41B-45B have hysteresis curves spaced apart in the manner described in connection with Figs. 4 and 5. The " ladle and bucket " ratio is 1 : 1 so that the first pair of forward and reverse driving pulses reverses the saturation of 41A and 41B in turn to produce positive output pulses from terminals 101, 102. The several pairs of cores are affected in sequence after which flip-flop 19 reverses and the process repeats with the B cores leading the A.