Patent GB-190421382-A (GB)
Title: A New or Improved Method of Operating Telephonic Exchange Systems and Apparatus therefor.
IPC: H04M1/02
Filed: 1904-10-05
Granted: 1906-01-05
Abstract: 21,382. Thomson, A. T. M., and Thomson-Davis Telephone System. Oct. 5. Indicators or annunciators; signals, indicator or visible.-Relates to telephone exchange systems of the type in which no verbal communication is necessary between the operators and the subscribers, the numbers of the subscribers wanted being indicated to the operators by means of numerical indicating - devices actuated through one of the line-wires. Assuming that the exchange is for a number of subscribers less than 10,000, each subscriber will have projecting from the case of his instrument four hand-levers 21, Fig. 5, by manipulating which he can set four number wheels 15 so as to indicate through windows in the case the number of the subscriber wanted. In doing so he causes each of the four sectors 19 to make contact with a certain number of contact-springs 13, of which one only is shown in Fig. 5. The springs 13 are connected by wires 12, Fig. 4, with contactstuds 10, over which an arm 8 is adapted to move when the detent 2 is withdrawn. The movement of the arm 8 is due to a coiled spring 1 which is wound up by means of the crank handle 4. While winding up the spring, after having set the number wheels 15, the subscriber earths his "B" line and gives a signal at the exchange. The response to this signal is the sending of a current which releases the detent 2 and allows the arm 8 to rotate. As it passes over the four sets of contact-studs 10, four sequences of currents are sent to the exchange through the " B " line, the number of impulses in each series depending on the setting of the number wheels. Each series sets one wheel of a step-bystep numerical indicator at the exchange, the intervals between the successive series allowing a sluggishly-acting relay at the exchange to transfer the second series to the " tens " number wheel, and so on. The detent 2 stops the rotation of the arm 8 after one revolution, but the exchange operator can again release the arm and repeat the call if there is any reason to doubt the reading of her indicator. The subscriber's bell is associated with an annunciator device shown in Figs. 10 and 11, and comprising a curved plate 27 bearing announcements such as "exchange called," " call received," "engaged," and " please speak." The annunciator plate bears a jaw ladder 30, between the jaws of which works a pin 31 on the bell hammer 33, so that a movement of the bell hammer may move the annunciator. In the act of winding up the spring of the number-transmitting apparatus, and thereby calling the exchange, an arm 3<a> on the spindle 3 lifts the rod 26 and lever 29, the latter acting successively on the pins 27<a>, 27<c> so as to lift the annunciator plate into its highest position and display the announcement exchange called." The rod 26 descends when the number-transmitting apparatus is released by the exchange operator, and the counterweight 27<d> descends until the first tooth of the jaw ladder is caught by the pin 31, the indication "call received" being then shown. The lever 29 at this time rests on the pin 27<e>. If the called subscriber is engaged, the operator sends a single impulse which causes the bell hammer 33 to move from its normal spring-held position so as to remove the pin 31 from the first to the second tooth of the jaw ladder, the indication " engaged " being then shown. If, however, the connection can be established, a series of impulses is sent to the subscriber's bell and the annunciator plate 27 assumes its highest position, shown in Fig. 11, the indication " please speak" being shown. In either case, the lever 29 is released from detention by the pin 27<e>, and as it falls the pin 29<b> breaks contact at 29<e> and disconnects the subscriber's " B " line from his signalling-apparatus. The numerical indicator at the exchange comprises four drums 45, Fig. 16, perforated to indicate the numerals, which are illuminated by lamps within the drums when all four have been set. The drums are spring-driven, through the toothed sectors 49, and their step-bystep movements are controlled by the electromagnetic escapements 54. After a call has been received, the operator re-sets the numerical indicator by lifting the arms 51 by means of the levers 60 and bar 59. The actuating-link 69 passes to a key within reach of the operator.