GB342681A - Improvements in and relating to electric signalling, controlling and measuring systems - Google Patents

Abstract

342,681. Frequency measurements. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Fitzgerald, A.S. ; 1212, Union Street, Schenectady, New York, U.S.A.) Oct. 3, 1929, No. 30022. Convention date, Oct. 4, 1928. [Class 37.] In a system for indicating at a distance the movements of a member, e.g. the readings of an indicating or integrating instrument, for measuring or comparing frequencies or for performing operations at predetermined frequencies, variable frequency derived from the movements &c. control thermionic valves which effect the charging and discharging of a condenser to produce current proportional to the frequency. The system may also be adapted to produce a summation indication of a number of independent instruments. As shown in Fig. 1, an indicating instrument 10 controls a condenser 15, 16 which varies the frequency of oscillation of a valve generator 11 according to the deflection of the instrument. At the receiver a transformer 28 is connected to the line wires 12 and has secondary windings 29, 30 reversely connected to the grids of negatively biassed valves 31, 32 in such a manner that the valves alternately pass current to charge and discharge a condenser 33 from a source 34. As shown the discharge current having a value proportional to the transmitted frequency is measured by a repeating instrument 13. Preferably a condenser is shunted across the instrument to smooth out pulsating current. To indicate the speed of rotation of an integrating meter a commutator adapted to interrupt a direct current source is driven from the instrument shaft and thereby generates pulsations the frequency of which is proportional to the speed. In order to render the repeating instrument independent of voltage variations in the source 34, the instrument may be of the "cross-coil" type, one winding being connected across the source, preferably in series with a resistance, while the other winding is connected in the indicating circuit. The repeating instrument may be provided with contacts in order that different circuits may be closed at different frequencies. Fig. 4 shows receiving arrangements for totalizing independent indications. Independent transmissions are effected over the line wires 12 and are indicated by the corresponding instruments 13 controlled by the valves 31, 32 supplied from the common sources 34, a totalizing instrument A being connected in the charging circuit of both receivers. The Specification as open to inspection under Sect. 91 (3) (a) states that the apparatus may be utilized to control synchronoscopes. This subjectmatter does not appear in the Specification as accepted.