Patent GB-348546-A (GB)
Title: A new and improved impulse transmitter or sender for signalling systems, telephone systems and the like
IPC: H04M1/274
Filed: 1930-02-12
Abstract: 348,546. Impulse transmitters. ERICSSON TELEPHONES, Ltd., 67, Kingsway, and DOIG, P., 19, Fordwych Road, West Hampstead, both in London. Feb. 12, 1930, No. 4747. [Class 40 (iv).] An impulse transmitter is adapted to be operated by detachable devices, e.g. keys, to transmit one or more trains of impulses characteristic of the form of the particular device used. As shown in Figs. 1 and 3, impulse transmitters K, T, U of known type are set to transmit characteristic signals when a key is inserted in a slot 3 and turned in the aperture 2 in the front plate 1 of the assembly. The particular signal transmitted depends on the form of the key used. The key slot 3 is located in a member 4, Fig. 5, loosely mounted on a spindle 5. Gear wheel assemblies 9, 10, 11 for setting the impulse transmitters are loosely mounted on the member 4. The assembly 9 consists of a bush 12 carrying a gear wheel 15, the bush and wheel having rectangular holes through which the operating key passes. The assembly 10 comprises a bushed disc 16, disc 17 and gear wheel 18, these components having keyholes shaped as shown in Fig. 10, the relative positions of the keyholes, when the assembly is in normal position, being as shown in Fig. 8. The arrangement of components and keyholes of the assembly 11 is similar to those of assembly 10. When a key 28 is inserted and turned to set the impulse transmitters the wheel 15 is rotated to its full extent to fully set the transmitter K, which may serve to identify a calling station, and the gear-wheels of assemblies 10, 11 are set to variable extents depending upon the form of the wards of the key which co-operate with the steps of the keyholes. At the end of the setting operation, the gear wheels of the assemblies 10, 11 are locked by weighted pawls pivoted on a shaft 48. Upon the release of the key after the setting operation, the spring of the impulse transmitter K drives the latter together with its associated assembly 9 back to normal during which a fixed train of impulses determined by the form of the impulse wheel is transmitted. When the assembly returns to normal position a striker 14 carried by the assembly operates the locking pawl of the assembly 10 to free the latter and allow its return to normal under the control of transmitter T which transmits an impulse train characteristic of the associated ward of the key. Similarly upon restoration of the assembly 10, the striker associated therewith releases assembly 11 and transmitter U sends a further characteristic train. The gear wheel assemblies are normally locked by a projection 32 on a pivoted lever 36 adapted to engage a slot in disc 33 and to be disengaged to free the assemblies when the key is fully inserted. The lever 36 when operated by the key operates contact set X which remains operated throughout the turning movement of the key by reason of the engagement of the projection 32 with the face of the disc 33. Further contact sets Y, Z, Fig. 3, are sequentially actuated during the setting movement by disc 33, the contacts X, Z remaining locked by a latch 42. Just prior to return to normal of the assembly 11 after signalling pin 19 effects the release of the contacts X, Z which if desired may be adapted to release in succession. Moreover if desired the latch 42 may hold one or both of the contact sets only partially operated. The contacts X, Y, Z may be employed for initiating operations whereby the line wires are extended to the apparatus for dealing with the impulse trains. More than one key may be used to determine the characteristic signal.