GB556855A - Synchronisation of alternating current sources particularly applicable to common wavelength broadcasting systems - Google Patents

Abstract

556,855. Automatic control systems for alternating current sources; phase changing. CALVERT, R. March 31, 1942, No. 4307. [Classes 38 (ii) and 38 (iv)] [Also in Group XXXVI] Oscillation frequency.-A source of oscillation is maintained in synchronism with a master oscillation by using two pairs of modulators essentially comprising rectifying means. The outputs from the modulators control in appropriate sense the frequency or phase or both of the controlled oscillation. The master oscillation may be fed to a transformer T1 with secondary windings e1 ... e4, respectively in series with rectifiers and condensers X1, C1 ... X4, C4. The controlled oscillation is fed to a transformer having secondary windings f1, f3. The condensers C1, C2 are connected in series in the grid circuit of a valve V1 and condensers C3, C4 similarly connected to a valve V2. The anode circuits of the valves include respectively relays A1, A2. The valves are normally biased to cut off by a voltage applied at 6. The modulators are poled as indicated and the normal vector relations of the voltages in the modulator circuits are indicated in Fig. 7. In these conditions no voltage appears between G and either P or Q. If the controlled oscillation begins to lead the master oscillation as indicated by the arrow in Fig. 7 P becomes positive to G and Q negative thereto the opposite change occurs with a lag. Thus the relays A1, A2 are selectively actuated to introduce into the circuit of the controlled oscillation a predetermined appropriate phase change # and to change the frequency of the oscillator by a predetermined amount when the relative phase of the oscillations has changed (substantially) by the angle #. Rapid fluctuations of the output voltages are ineffective due to smoothing condensers C. Static phase shifting circuits capable of a progressive change of the phase angle in either sense are controlled by the relays. Standard Post Office rotary line switches may be connected to resistances in resistance-condenser circuits and racked round by the relays. The relays also control a reversible motor adjusting a tuning element to change the frequency of the controlled oscillator. The Specification contains a full description of the arrangements. The Provisional Specification describes also an arrangement employing only two modulators and has relays which operate in a different order according to the sense of deviation ; this subject-matter is not claimed.