Patent GB-652606-A (GB)
Title: Improvements in or relating to electric wave generators
IPC: H03K3/543
Filed: 1947-02-21
Abstract: 652,606. Pulse delaying circuits. WESTERN ELECTRIC CO., Inc. Feb. 21, 1947, No. 5139. Convention date, Feb. 28, 1946. [Class 40 (vi)] In a step wave generator in which a storage capacitor is discharged into a transfer capacitor, the potential across the storage capacitor is used to modify the potential applied to the transfer capacitor so that the charge transferred is maintained constant. The effect of the internal impedance of the pulse source feeding the generator is compensated to produce square steps. The circuit is described as applied to a pulse delaying circuit in which a pulse is emitted delayed with respect to a " zero " pulse, the delay being variable in ten microsecond intervals. Crystal oscillator-Pulse producing circuit, Fig. 2. Valve 211, stabilized by crystal 210 operating at 100 kc/s. feeds sine waves to valve 212, biassed beyond cut-off, the output being applied to valve 214 to produce square waves in line 216, Fig. 9 (not shown). The cathode of valve 212 supplies normally non-conducting valve 215, to produce short, negative pulses on line 218. Step waveform generator, Fig. 3. Transfer capacitor 308 is charged over the left half of diode 303 during the positive half of the square wave on line 216, and is discharged through the right half by charge flowing from the storage capacitor 310 in the succeeding negative halfcycle, thus developing a negative-going step waveform, Fig. 8 (not shown). In order to maintain constant depth of step, the cathode of the left-hand diode is returned to valve 304 which operates as a cathode follower. The abruptness of the fall in grid potential of valve 304 is ensured by including a resistor 311 in series with storage capacitor 310. When the potential of cathode of valve 304 has fallen sufficiently, the normally non-conducting right side of valve 305 passes current causing flip-flop 306, 307 to reverse, valve 307 being rendered conducting to emit a negative pulse to the next counter, Fig. 4 (not shown). When valve 306 is cut off, the left side of triode 305 is rendered conducting to recharge capacitor 310, the rise in potential causing, through cathode follower 304, the right side of valve 305 to be rendered non-conducting. Valves 306, 307 are not affected but return to normal after a delay governed by the constants of the cross-coupling. This is made equal to about half a step, the valve 307 being rendered conducting to terminate the pulse fed to the next counter. A feedback capacitor 313 removes the effect of the spurious pulse which would otherwise be produced when flip-flop 306, 307 reverts. The resistor 330 improves the steepness of the potential wave fed to valve 304 when capacitor 310 recharges. The ten steps of the first counter occur at ten micro-second-intervals, the five succeeding counters each operating at one-tenth of the speed of the preceding counter. Initiating and zero pulse generator, Fig. 5. One of the step waves is selected by switch 502, differentiated and fed to normally non-conducting valve 504 to supply a negative-initiating pulse to line 507 feeding the pulse generating circuits. The negative pulse, fed over diode 522 causes the trigger pair 520, 521 to reverse. The next pulse on line 218, occurring seven and a half micro-seconds later, causes the trigger pair to revert to normal, the positive pulse occurring when valve 521 is rendered non- conducting being fed to non-conducting valve 524 to produce a positive " zero " pulse at the cathode and a negative pulse at the anode. Valve 541 is a buffer stage for monitoring purposes. Pulse generating circuits, Fig. 6. The negative initiating pulse on line 507 is applied over diodes 650 to reverse the trigger pair 651, 652, the positive pulse from the anode of valve 652 operating the indicator 653. The negative pulse from valve 651 cuts off valve 647 in the chain 640 ... 647. These valves share a common anode load 670 and maintain a low anode potential while any one is conducting. Valves 640, 645 are biassed over potentiometers 620 ... 625 and are fed from the six step wave generators, each valve continuing to conduct until the step-is reached corresponding to the numbered position of the potentiometer wiper. As shown, one or more of the valves will continue to conduct until 5.58475 seconds have elapsed after the zero pulse. The next pulse on line 218 renders valve 646 non-conducting, whereupon the anode potential of valves 640 ... 647 rises to initiate positive and negative pulses from normally non-conducting valve 654. The fall in screen potential is fed over diode 651 to reset the trigger pair 651, 652, the rise in anode potential of valve 651 switching on valve 647, thus causing valve 654 to cease conducting to terminate the output pulse.