Patent GB-370041-A (GB)
Title: Circuit arrangement for telegraph exchange system
IPC: H04L12/04
Filed: 1931-01-02
Abstract: 370,041. Telegraph exchange systems. BERRY, R. J., Telephone Building, The Hyde, Hendon, London.-(Lorenz Akt.-Ges., C. ; 1, Lorenzwed, Tempelhof, Berlin.) Jan. 2, 1931, No. 166. [Class 40 (iii).] In a telegraph exchange system in which signalling is effected by breaks in a subscriber's line circuit, a second circuit provided at the central station for the subscriber is adapted to be closed automatically on interruption of the original closed circuit on making a connection, and not to be opened after the cessation of signalling until closure of the original closed circuit upon disconnection of the subscriber from the exchange. When a subscriber Tn wishes to communicate with a subscriber Tnl of the exchange VM, he depresses a key T opening the closed current circuit extending over relays AR and ER and starting his motor. Relay AR de-energizes, illuminates a calling lamp AL at the exchange, and at its contact 1ar closes again the current circuit through the relay ER. On the insertion of an answering plug AS into the jack Kl, the circuit of the relay ER is broken at contact 1, and at contact 9, the relay AR is energized to open at its contact 5ar, the circuit of the lamp AL, but not before an exchange battery LB has been connected over the relay LR1 to the plug AS to form a new closed circuit for the subscriber Tn when the contact 6er is released. At contact 8lrl the circuit of a control relay STRI is interrupted, and at 10lrl a circuit is prepared for a slow-release relay VR. On the insertion of the calling plug VS into the jack Kl1 of the desired subscriber the circuit of a relay ER1 is opened at contact 7, a relay AR1 is locked up over contact 10, and the relay VR is energized over the released contact 9er1. The closed current circuit of the called subscriber Tnl is opened at the contact 11 vr, and his telegraph apparatus set into operation. A relay UR switches over the connection between Tn and Tn1 at the contact 13ur and at contact 7ur opens the circuit of the relays LR1 and VR. The telegraph transmission takes place by current interruptions in a closed circuit containing the relay LR2, whose contact 13lr2 is normally in the energized or left-hand position. In the normal position of the contact 13lr2, a circuit is completed for a flywheel relay 1 R whose contact 20 ir is arranged to be slow to close and which effects at contact 14ir the intermittent operation of a relay 1VR. At the contact 15ivr a control relay STR2 is intermittently energized and steps up a ratchet mechanism tending to close a contact 17 str1. During the signal transmission the intermittent release of the contact 13lr2 to the right-hand position energizes a control relay STR1 which releases the ratchet mechanism stepped up by the relay STR2. When signal transmission is discontinued for a predetermined time the relay STR1 is no longer energized but the relay STR2 is intermittently operated and the ratchet mechanism stepped up so that, after a certain time, the contact 17str1 is closed. A relay SR pulls up and effects at contact 18sr the illumination of a clearing lamp SL and at 13sr the release of the relay UR. At contact 13ur the telegraph connection between the subscribers is broken, and at 16sr the circuit of the relay STR1 is opened. Relays LR1 and VR are operated and closed current circuits are again established for the subscribers Tn, Tn1. If either subscriber resumes the telegraph transmission before the connection is broken down by the exchange operator, one of the relays LR1, LR2 is released, and over contact 17vr the control relay STR1 operates, releases the ratchet and pawl mechanism, and opens the contact 17str1. Relay SR falls off, the clearing lamp is extinguished, and relay UR responds over released contact 13sr, to complete at contact 13ur the telegraph connection between Tn, Tn1. In breaking down the connection at the exchange by the withdrawal of the plugs VS and AS, the contacts 4, 7 and 1, 3 of the jacks Kl1, Kl respectively make before break so that closed current circuits of the subscribers Tn, Tn1 are reestablished to prevent the operation of the motors driving their telegraph apparatus. Specification 284,740, [Class 40 (iii), Telegraphs, Electric], is referred to.