GB398871A - Improvements in or relating to methods of synchronising television apparatus - Google Patents

Abstract

398,871. Television. FERNSEH AKT.- GES., Goerzallee, Zehlendorf, Berlin. March 21, 1932, No. 8376. Convention date, March 27, 1931. [Class 40 (iii).] In a television system in which all or a portion of the receivers have motors fed from the same mains as the transmitter motor, more accurate synchronization is effected by the provision at the transmitter and/or any or all of the receivers of means for keeping constant the phase of such motor or motors. In practice it is found that this phase constancy is maintained with sufficient accuracy by keeping constant the terminal voltage of the motors, e.g. by inserting between the mains and the motors any known form of automatic control for this purpose. In the system illustrated diagrammetically in Fig. 1, the network 2 is supplied with alternating current from a station 1 and feeds both the motor 3 driving the picture analyzing device 4 at the transmitter and also the motors 5 driving the picture composing devices 6 at the receivers. When such a system is complete in itself, the phase or voltage either of the motor 3 or of the motors 5 or of both may be maintained constant ; when, in addition, there are other receivers not connected with the network 2, e.g. the receiver 10 incorporating a synchronized direct current motor 9 supplied from a station 7 through a network 8, it is necessary to maintain constant the phase or voltage of the transmitter motor 3. The known devices employed for keeping constant the terminal voltages of the motors 3, 5 may comprise iron-hydrogen resistances, Fig. 2 (not shown), inserted between the mains and motors, chokes, Fig. 3 (not shown), having air-gaps of varying widths, or adjustable resistances acting on the Tirril principle. According to the Specification as open to inspection under Sect. 91 phase correction of the motors may be effected by selenium or photo-electric cells at the receivers operating in conjunction with synchronizing signals from the transmitter. This subject-matter does not appear in the Specification as accepted.