Patent GB-365142-A (GB)
Title: Improvements in and relating to telemetering systems
IPC: G08C15/10
Filed: 1930-10-03
Abstract: 365,142. Electric signalling systems. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Franklin, C. S. ; 1736, Van Ness Avenue, Hollywood, California, U.S.A.) Oct. 3, 1930, No. 29657. Convention date, Oct. 5, 1929. [Class 40 (i).] In a method of indicating at a distance the readings or conditions of a number of meters or other elements, in which current impulses are transmitted through a channel of communication to a distant station, each impulse having a characteristic in accordance with the condition of an element to be remotely indicated, and the impulses being separated by predetermined time intervals, means are provided responsive to the interruptions between impulses for successively connecting a number of indicating devices to the channel of communication, and means are provided for ensuring that each device is connected only during its appropriate impulse. In the construction shown in Fig. 1, a line 1 comprises the conductors of a power distribution system over which carrier current impulses are transmitted in succession, each impulse being modulated with current having a frequency determined in accordance with the position of a movable element at a remote transmitting station. These currents are impressed upon the grid of an electron discharge detector 3. The resulting anode currents are supplied to receiving instruments 7, 8, 9, &c. depending upon the position occupied by switch elements 5, 6. The instruments 7, 8, 9, &c. comprise frequencyresponsive indicating devices, each of which responds to the frequency of current with which the corresponding received carrier impulse is modulated. The elements 5, 6 form part of a selector switch 12 adapted to be stepped by de-energization of a magnet 13. The magnet is controlled by means of relays 15, 16, 17, the relay 16 being slow to release. With the apparatus in the position shown, transmission of a current impulse causes an increase in the anode current of the detector 3, whereby relays 15 and 16 are energized. Also the instrument 7 will give an indication in accordance with the characteristic of the impulse. When the carrier is interrupted for a predetermined interval, two circuits will be completed due to the slowreleasing character of relay 16, one circuit through the winding of magnet 13, and the other through the winding of relay 17. This relay, after a certain interval, attracts its armature, thereby opening the circuit through magnet 13, so that the switch 12 acts to connect the instrument 8 to the carrier channel. When the next impulse is received the armature of relay 15 will again be attracted so that relay 17 is de-energized, but the armature of relay 16 remains unchanged. The interruption of the carrier causes a repetition of the cycle of operations, the instrument 9 being connected to the carrier channel. Each of the receiving meters is thus connected to the carrier channel prior to the initiation of its corresponding carrier impulse. When the carrier is interrupted for an interval longer than the intervals between the various signalling impulses, relay 16 de-energizes whereby a circuit is completed through the upper wiper of switch 12 and its co-operating bank of contacts, and through magnet 13, whereby the switch 12 is stepped round to its normal position. In the modification shown in Fig. 2, the connection of the receiving instruments to the receiving channel is indicated by means of lamps 7<1>, 8<1>, &c. During the first carrier impulse relay 15 is energized causing the energization of the slow-to-release relay 19. When the carrier is interrupted a circuit is completed through the windings of relay 20 and magnet 13 connected in parallel. Relay 20 operates to disconnect the meter 7 from the carrier channel. When the next impulse is received magnet 13 and relay 20 are de-energized, the magnet 13 causing the instrument 8 to be connected to the carrier channel, and the relay 20 after a short interval completing the circuit of the instrument 8. When the position of all the remote elements has been indicated a long interruption occurs whereby relay 19 is de-energized, and a circuit is completed through the upper wiper of selector switch 12 and the magnet 13, so that the switch is stepped round to its normal position. Specification 293,027, [Class 40 (i), Electric signalling systems &c.], is referred to.