Patent GB-250940-A (GB)
Title: Automatic telephone exchange system
IPC: H01H67/26
Filed: 1926-04-12
Abstract: 250,940. Gfeller Akt.-Ges., C. April 15, 1925, [Convention date]. Automatic exchange systems; selectors.-In a small system in which a cross-bar device is used as the connecting means, each subscriber is allotted a horizontal bar zu<1> adapted to be moved by a horizontal magnet M<30>, whilst sliding vertical blades St<1> corresponding in number to the number of possible simultaneous conversations are adapted to be lifted by pawls Kli<1>, Fig. 2, operated by stepping magnets H. At each point of intersection four pairs of contacts du and two contact-closing strips He<1>, He<2> are provided, each strip being adapted to operate two contact pairs, the lower pair being used when a subscriber is calling and the upper pair when he is called. On the lower end of each blade St' are carried sequence switch brushes Kfd which wipe over contacts Kdg. The blades St<1> are provided at intervals along their length with oblique lugs and notches which co-operate with the strips He<1>, He<2> in the following manner. It is arranged that one of the blades St<1> is always in position 2 in readiness for completing a connection. When a subscriber calls, his horizontal magnet M<30> is energized and moves its bar zu<1> to the left, thereby actuating auxiliary contacts W<30> and causing the strips He<1>, He<2> at each horizontal point to be brought into operative relation with the lugs on the vertical blades St<1> by stops Mi<1> on the bar zu<1>. The blades St<1> and sequence switch Kfd are now raised to position 3 during which movement the strip He' is engaged by a lug on the blade St' and moved through a respective notch to the left-hand side of the blade, thereby closing the lower contact pair du. In this extra movement the strip He<1> engages a stop Mi<2>, Fig. 3, on a parallel bar Zu<2> which is moved to the left to open auxiliary contacts p. The stepping magnet H is now connected up and when the calling party dials is lifted to a position in which the magnet M<11> of the called party is energized over the sequence switch Kfd, and moves the horizontal bar to displace the strips He', He<2> and actuate contacts W<11>. The blade St<1> is raised to position 11 and during this movement the strip He<2> of the wanted party is engaged by a lug on the blade St<1> and passes to the lefthand side closing the upper called contact pair du, and opening the auxiliary contacts p through the parallel bar. Fig. 8 shows a circuit arrangement for a small exchange of seven subscribers. When a subscriber removes his receiver to make a call his horizontal magnet M and a starting relay Aa are energized. The magnet M moves the bar zu<1> to bring the strips He<1>, He<2> into their operative positions, whilst relay Aa closes a circuit over bridging wipers I of the sequence switch Kdg of the first disengaged connecting blade St (in its prepared position 2) for its stepping relay F, which energizes the stepping magnet H to raise the blade St to position 3 in which a notch No engages the strip He' which is moved to close the lower pair of contacts du. At the same time the rod zu<2> opens contacts p to de-energize magnets M, Aa. In position 3, a circuit is closed over lead 3 and lead 4 of the next blade assembly (in position 1) for its relay F which energizes the magnet H to step the blade into its prepared position 2. Returning to the connection, the closure of contacts du connects the calling line to battery over a line relay A which energizes a slow-release relay V, which prepares the impulsing circuit for the stepping magnet H. The calling party now sends a series of impulses which are repeated by relay A to the magnet H. At the end of the impulses a prolonged interruption causes the relapse of relay V to close a circuit over P, p<2>, v' and the contacts bridged by the arm II of the sequence switch in its selected position, for the horizontal magnet M of the wanted party, which moves its rod zu<1> to close contacts w and complete a locking circuit for magnet M in series with relay Aa. Relay P opens the original circuit of magnet M, locks over blade springs S, and closes a circuit over bridging arm I for stepping relay F which causes the blade St to be advanced through any further selective positions to position 12. In passing from position 11, a notch No engages the strips He<2> of the called party. The upper contact pair du are closed and contacts p opened, thereby preparing the called party's talking circuit and denergizing his magnet M. In position 12 relay P is de-energized at the blade springs S, and ring- ing current from the source U interrupted by relay R is sent over bridging arm III to the called line. When the wanted party answers relay F is energized over back contacts r and drives the sequence switch to position 13 in which the talking circuit is completed, the parties being fed over relays A and Y. When the calling party hangs up, relays A, Y relapse, between their deenergization an impulse being sent through the magnet H to advance the blade St to its final position 14 in which a pin on the blade trips the holding pawl Kli<2>. The blade St now falls under gravity and the selector elements restore to normal. The pawl Kli<2> has two resting positions and in the normal position of the blade St another pin on the latter trips it to its operative position. Co-ordinate selection can be provided for by connecting each selective position of the switch Kda to a group of subscribers' magnets M. The Specification as open to inspection under Sect. 91 (3) (a) states that in this case the second series of impulses energizes the magnets of the selected group in succession, each when energized opening the circuit of the preceding one. This subject-matter does not appear in the Specification as accepted.