Patent GB-646929-A (GB)
Title: Improvements in or relating to control circuits for electrical oscillation generators
Inventor: WHITE ERIC LAWRENCE CASLING
IPC: H03L7/12
Filed: 1947-07-04
Abstract: 646,929. Automatic control systems. ELECTRIC & MUSICAL INDUSTRIES, Ltd. July 4, 1947, No. 17641. [Class 38 (iv)] [Also in Group XL (c)] A control circuit for oscillation generators, of the kind in which the phase is compared with that of master oscillations, and the resulting output voltage utilized to adjust the frequency of the generator, is provided with further means also responsive to phase difference for changing the magnitude of the control voltage whenever a particular phase difference recurs. As shown in Fig. 1, the controlled generator 1 and the master source 2 feed directly into a mixer 4, the output voltage, representative of phase difference, being applied to the grid of a valve amplifier 7. A control voltage is fed from the anode circuit of the valve 7 to the grid of a reactance valve 3 for adjusting the frequency of the generator 1. The master oscillation is also fed through a quadrature phasing network 12 to a mixer 11 which receives oscillations directly from.the source 1. If the two oscillators 1, 2 are operating at different frequency, beat oscillations in phase quadrature are produced at the output of the mixers. These are applied to the grids of valves 14, 21 to operate intermittently the relays 15, 22 and so to swing the contact arms 16, 23. The sequence in which these arms operate is dependent on which of the beats has the leading phase, and this is dependent on which of the sources 1, 2 is running the faster. If arm 16 is on contact 18 when arm 23 is on contact 24, a negative charge is fed from source 20 into a condenser 26, and the subsequent movement of arm 23 to contact 25 applies a negative pulse to the grid of the valve 7 which is transferred as a positive pulse to the reactance valve 3 and adjusts the frequency of the source 1 in the corrective sense. Further control pulses are applied at each cycle of the beat frequency until the frequencies of the sources 1, 2 are in agreement, any subsequent adjustment for phase being provided by the output of mixer 4 acting directly on the grid of the valve 7. If the frequency drift is in the opposite sense to that described, a positive voltage is transferred from the source 19 through contact arms 16, 23 to the condenser 26. The anode of the valve 7 is connected through resistor 8 to a positive point and through resistor 9 to a negative point. A tapping on the resistor 9 connected to the reactance valve grid has also a negative feedback connection to the grid of the valve 7 through a condenser 28 and a parallel-connected resistor 29 and condenser 30 for the purpose of linearizing the valve operation. The charge on the condenser 26 is fed to a point between the condensers 28, 30. In a modified arrangement, the parts 14 ... 20 of Fig. 1 are omitted, and the output voltage from the mixer 4 is fed to the grid of one valve of a cathode-coupled valve pair 14a, 14b, Fig. 3, the other valve having a tapped resistance 40 associated with its anode which provides either positive or negative voltage for charging the condenser 26 according to the sign of the mixer output. The mixer circuits may be of the kind described in Specification 534,749.