Patent GB-366711-A (GB)
Title: Improvements in apparatus for measuring characteristics of electric impulses
IPC: H04M1/24
Filed: 1931-01-29
Abstract: 366,711. Impulse transmitters; automatic exchange equipment. ERICSSON TELEPHONES, Ltd., 67, Kingsway, London, and ROBINSON, E., 46, Ella Road, West Bridgford, Nottingham. Jan. 29, 1931, No. 2872. [Class 40 (iv).] The characteristics of electric impulses, e.g. the ratio of make to break, is measured by the movement of a driven member which is coupled to a driving member during the occurrence of elements of one kind, e.g. make or break. The invention is particularly applicable to the measurement of impulses generated by a sender or by a dial transmitter in automatic telephony, and may be used to measure impulses comprising light and heavy current, reversal of polarity, or different kinds of current such as D.C. and A.C. In one arrangement, the apparatus is designed to be attached directly to a dial transmitter, while in a second arrangement it forms part of the exchange testing equipment and measures impulses transmitted from a distance. First arrangement, Figs. 1 and 3, in which the tester is directly attached to a standard dial transmitter. The transmitter is detachably secured to a mounting board MB in the manner in which it is secured to the usual dial holder, and the impulse terminals make contact with springs on the board. An electromagnetic clutch, Fig. 3, is carried by a base member 11 which is secured in the central recessed position PL of the finger plate by fixed projections 12 and a spring catch 13, 15, A clutch plate 16 of magnetic material and carrying a pointer PR is fixed on a spindle 17 which passes loosely through the base 11 and is held in position by nuts 18 and spring 19 which is adjusted so that the plate 16 normally rotates with the finger plate. The plate 16 may be slightly dished and plated with copper &c. to assist quick release by the magnet, and a fibre disc 27 may be interposed between it and base 11. The magnet M comprises a casing 23 and hollow core 21 loosely mounted on spindle 17, the leads being taken through a tube 25 to terminals 26 which engage springs 28, 29 on the mounting board when the clutch is placed in position. The mounting board may be hinged at H1 to enable the impulse springs to be adjusted without removing the dial. The impulse circuit comprises the impulse springs connected in series with the clutch magnet, key KY, and terminals T1, T2 which are connected to battery. A spark-quenching condenser QA may be connected across the springs. The operator presses key KY and dials "O." The clutch plate 16 is carried around with the finger plate until pointer PR engages a stop 30. On return of the finger plate, magnet M is energized except during break periods so that the pointer moves only during these periods and the ratio of make to break may be read on scale S and is independent of the speed of impulsing. Second arrangement, Figs. 6 to 8, in which the transmitter is tested over subscriber's line. The tester comprises a shaft 33 carrying two electromagnetic clutches M1, M2, similar to the clutch previously described, the shaft being driven at constant speed by a motor MR controlled by governor G. The plates 32, 31 of the clutches rotate with a shaft member 34 when M1, M2 are de-energized and carry pins 41, 42 which operate off-normal spring sets ON1, ON2. Rotation of the magnets is prevented by the engagement of pins 39 on the magnets with fixed brackets 40. The electrical connections are made over a terminal strip TS. Controlling apparatus, Fig. 8, may form part of test-desk equipment. The operator plugs jack J of subscriber's line, whereupon impulse relay A pulls up, it being assumed that a linesman is on the line at the substation. Relays B and MS energize and motor MR is started, and assuming that the pointers are not at zero, clutch magnets M1, M2 energized over wiper rs1, rs2 of rotary switch RS are released by pressing key RK so that the pointers are driven to zero in which position the magnets are again energized over off-normal springs ON 1, ON2 and the pointers are held. The operator connects his speaking set OT to line over key K2 and requests the linesman to dial "O." The rotary switch is driven by a back stroke magnet and takes its first step when A re-operates after the first break. Magnet M1 holds over rs1 during the make period but M2 de-energizes and remains so until the end of the train so that pointer PR2 moves on steadily. Magnet M1 is released during the break periods so that pointer PR1 carried by clutch plate 31 moves during these periods. At the end of the train, RS has taken ten steps, M2 pulls up over rs2 and holds pointer PR2 which has thus moved through an angle corresponding to nine make and break periods while PR1 has moved through an angle corresponding to nine break periods. The glowing of lamp L (indicates a correct number of impulses. PR1 gives a correct ratio reading provided the driving shaft has run at the specified constant speed and the impulsing speed is standard. If impulsing speed or shaft speed departs from standard, PR2 indicates a correction factor for the ratio reading. If the conditions are such that a unity correction factor is indicated, pointer PR1 gives a true reading although some conditions are not standard. To repeat the test, RK is thrown with results as before and, in addition, RS steps to the next normal position over RK3. The switch also goes to a normal position if the line circuit is permanently opened.