Patent GB-357521-A (GB)
Title: Circuit arrangement for telegraph installations with selector working
IPC: H04L12/00
Filed: 1930-06-13
Abstract: 357,521. Telegraph exchange systems. SIEMENS & HALSKE AKT.-GES., Sicmensstadt, Berlin. June 13, 1930, No. 18202. Convention date, July 16, 1929. [Class 40 (iii).] In a telegraph system in which the connection between two subscribers is established through one or more exchanges by automatic selectors, the calling line is switched over to an exchange telegraph apparatus if the called subscriber or the outgoing line to a further exchange is engaged and the message is transmitted to the exchange apparatus. When the engaged subscriber or line becomes free the message is forwarded by an operator from that exchange at which the connection was switched over. When a calling subscriber of an exchange A dials impulses particularizing an exchange B and a group selector GW finds a free line VL, a polarized relay ER through its contact 1er energizes a polarized relay ER1. At the contact 6er1 a relay Rl is energized and at its contact 7r1 places a negative potential on the line a1. Through the contact 9r1 the selector in which the lines a1, b1 end is engaged, and places a negative potential on the line b1 effecting the operation of relays ES1, X1, ES and R in sequence. Through the contacts 5es and 3r a negative potential is placed on the line b, and a free signal is transmitted to the calling subscriber, who now dials the number required. If the desired line is engaged, a positive potential is placed on the line b1, and relays ES1, X1, ES are deenergized. The release of relays ES transmits an engaged signal to the calling subscriber. The operation of relays R1 and X1 had energized a relay Y1, which at its contact 14y1, closed a holding circuit independent of the subsequent de-energization of the relay X1, through which at the contacts 13x1, 15y1 the relay An1 is energized. Through the contact an1, the relay C1 of an idle finder AS is operated, and closes at contact 21c1 a selfinterrupting circuit for the rotary magnet D1. On engaging the third contact, as shown, the relays P1 and U1 open at 26p1 the circuit of the magnet D1 and at contacts 24p1, 25p1, 17u1, 18u1 switch the line VL through to the exchange telegraph apparatus StA. A relay EA is energized and starts the apparatus, of which a relay S (not shown) operates a contact s to place a negative potential on the line b, through which a free signal is transmitted to the calling subscriber. The message is now transmitted to the relay EA of the exchange apparatus StA. On breaking the connection, a positive potential is placed on the line a, de-energizing the relays ER, ER1, R1, and causing Y1 and EA to drop. Contact s is reversed, and relays ES1, X1, E5 and R are de-energized, opening at 12x1 the circuit of relays U1, P1, and the line finder is now free for another call. In a modified arrangement, Fig. 2 (not shown), connection can be established in both directions through exchanges, each of which includes a switch gear which is stepped forward by the dialling impulses and discriminates between calls for subscribers of the exchange and those for subscribers of a further exchange. If the called subscriber line or a selector or an outgoing line for establishing the connection to a further exchange is engaged, the calling subscriber is switched over to the telegraph apparatus of the exchange reached, a signal indicating the name of the exchange being transmitted to the calling subscriber when the apparatus is taken into use, by an arrangement as described in Specification 342,479.