Patent GB-190823888-A (GB)
Title: Improvements in Automatic Exchange Telephone Systems.
Inventor: HILDEBRAND PAUL
Filed: 1908-11-07
Granted: 1909-10-28
Abstract: 23,888. Hildebrand, P. Nov. 7. Telephone systems.-In an automatic exchange telephone system, each subscriber is provided at the exchange with a switch having contacts for all the other subscribers to the exchange, and the contacts of the different switches are connected together in pairs in such a way that in order to establish a connexion between two stations, the exchange-switch of the calling-subscriber is moved to the contacts of the subscriber required, and then the exchange-switch of the latter subscriber moves automatically to the contacts of the calling subscriber, the connexion being thus established through the switches of both the subscribers. The subscriber's apparatus comprises the usual telephone apparatus a, b, Fig. 1, a bell c, a relay 125 controlling the bell, an impulse-transmitter d, a six-position rotary switch e controlled by the magnet 8, and a similar six-position switch f. The exchange-apparatus comprises a switch i, Fig. 2, for each subscriber, the switch-arms 13, 14 of which can be rotated over pairs of contacts 10, 10<a>, 20, 20<a>, and so on, leading to the switches of the other subscribers, by means of a magnet 17 responsive to the selecting-impulses sent through the line-relay 19 or by means of a self-interrupting magnet 18. The contacts 20, 20<a> of switch No. 10 are connected to contacts 10, 10<a> of switch No. 20 and so on. The subscriber's exchange apparatus also includes a six-position rotary switch k<10> and a similar four-position switch l<10>controlled respectively by the magnets 37, 22. The rotary arms of the switches e,f, k<10>, l<10> are designed to connect the outer one of the concentric contacts with the diametrically-opposite inner contact, and the function of these switches is to prepare and interrupt the circuits for the selecting-impulses and for the ringing and speaking currents. The operation of the system, briefly described, is as follows :-When subscriber No. 10 desires to connect with station No. 20, he first turns the contact-arm 3 of his impulse-sender d to contact 20, and then releases it by depressing the stop 6, whereupon it is returned slowly to its normal position by clockwork &c. On turning the arm 3 to the right, a momentary contact 23, 24 completes the circuit of a magnet 27, moving the switch f into its second position, and thus preparing a circuit which is afterwards completed at 31, 32 through the magnets 8, 37 whereby the switches e, k<10> are moved into their second position, the switch k<10> preparing a circuit for the selecting- impulses which pass from the impulse-sender d over the line-wire II, the contacts 52, 53 of the switch k<10>, the contacts 54, 55 of the switch l<10> and through the relay 19 to the battery m and the calling-station. The switch-arms 13, 14 are thus moved by the magnet 17 on to the contacts 20, 20<a>. When the impulse-sender d returns to its zero position, the contact 65, 66 closes a further circuit through the magnets 8, 37, and through the magnet 22 associated with the switch l<20> of subscriber No. 20. The switches e, k<10> are moved into their third position and the switch l<20> is moved into its second position, thereby completing the circuit of the magnet 18, which steps round the switch of subscriber 20 until its contact-arms engage the contacts 10, 10<a> of the calling subscriber, whereupon a circuit is established which moves the switches e, k<10> into their fourth position and the switch l<20> into its third position, thereby cutting-out the magnet 18. When the switches i move from their zero positions, the central metallic part 16 is lowered and breaks the contact which normally exists between it and a number of springs connected to the contacts 10<a>, 20<a>, 30<a>, &c., thereby preventing interruption by another calling subscriber. When a connexion has been established, the calling subscriber's bell rings, and he then removes his receiver thereby completing a circuit through the relay 125 of the called subscriber, this relay completing the bell circuit. When the called subscriber removes his receiver, the telephone instruments are substituted for the relay 125 and conversation can take place. When the receivers are again hung up, further circuits are established whereby the switches e, f, k<10>, l<10> and the main switches i are returned to their normal positions.