GB460997A - Improvements in or relating to systems for the teletransmission of indications of meters or like devices - Google Patents

Abstract

460,997. Electric signalling systems. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. June 7, 1935, Nos. 16662 and 16663. Convention dates, June 8, 1934 and May 4, 1935. [Class 40 (i)] [Also in Group XL] In a system wherein the indications of a meter are transmitted by currents of a variable frequency derived from the algebraic sum of a constant frequency and a frequency corresponding to the indication, the variable frequency modulates a carrier wave to operate a receiving apparatus wherein the constant frequency component is removed. The modulations are produced by a photo-electric cell 17 subjected to a beam of light which is interrupted by two discs 5, 8. The disc 5 is driven by a meter 1 and has apertures 6 whilst the disc 8 has teeth 12 and is driven at constant speed by a synchronous motor 10. The combined effect of the apertures 6 and teeth 12 produces a sinusoidal current in the cell 17. In a modification, the disc 5 is driven by the planetwheel of a differential mechanism, one wheel of which is driven at constant speed and the other by the motor. Several transmissions relating to different quantities may be effected simultaneously ; the different quantities may employ the same frequency band, each band modulating intermediate frequency waves peculiar to the several quantities which then modulate a single carrier wave ; alternatively different frequency bands which modulate a common carrier may be employed. At the receiver, a synchronous motor is operated by the incoming signals and the constant component is removed by a clockwork or synchronous motor through differential mechanism. An apertured disc may be operated at the resultant speed to control a photo-cell which is connected to a frequency meter. The indications of a plurality of transmitting instruments may be summated at the receiver by differential mechanisms. The Specification as open to inspection under Sect. 91 states that indications may be given by the receiver synchronous motor alone. This subject-matter does not appear in the Specification as accepted.