Patent GB-443313-A (GB)
Title: Improvements in and relating to automatic connection exchanges, e.g., telephone exchanges
IPC: H04Q3/00
Filed: 1935-02-13
Abstract: 443,313. Automatic exchange systems. RICHTER, M. B., (trading as TELEFONFABRIK AUTOMATIC VED M.B. RICHTER), 7, Amaliegade, Copenhagen. Feb. 13, 1935, No. 4679. [Class 40 (iv)] In a small exchange in which calling and called parties are directly connected by relays to the same or opposite ends of a common feed circuit, a selecting device acts first as a call finder to operate the connecting relay of the calling party and then under the control of impulses to operate that of the called party. Four arrangements are described in three of which the selecting device is a step-by-step switch whilst in the fourth a relay group is employed. The fourth arrangement comprises means for calling a party absent from his telephone, for operating an annunciator to summon an attendant, for initiating certain operations such as switching on a motor or a radiator, and for establishing calls to or from a main exchange. Incoming mainexchange calls may be answered by any subscriber and transferred if necessary to a particular wanted party. First arrangement, Fig. 1. When subscriber AB2 removes his receiver, common line relay Str, which has a winding for each subscriber, operates and starts switch V. When the calling line is reached relay Pr operates over wiper V2 in parallel with Str to stop the switch, and the calling-subscriber's connecting relay Abr 2 is operated over wiper V1 and locks over contacts of a holding relay Kr. The calling line is now connected over conductors 5 to line relay Ar and the switch V is released and set again by impulses. If the wanted line AB1 is free, relay Cr operates connecting ringing relay Rr over wiper V1 in series with the called-subseriber's connecting relay Abr1. If the called subscriber is to the right of the calling subscriber as in the present example, a discriminating relay Or is operated to restore the connection of AB2 to relay Ar which was interrupted by the operation of Abr1 and to connect the ringing source to the called line. When the called party replies, his feed relay Br operates and cuts off ringing. Second arrangement, Fig. 2. The operation is in general similar to that described with reference to Fig. 1, but during conversation both subscribers are connected in parallel to a common feed relav Ar over contacts of connecting relays Abr 1, Abr2, and individual line relays Aar1, Aar2. The line relay of the calling subscriber is first operated directly over the loop, is then locked over the loop in series with start relay Str, and is subsequently held over a second (left-hand) winding in series with the corresponding connecting relay. Ringing-current is supplied to the called party over back contacts of his line relay which is short-circuited until the called party replies by battery over wiper V1 connected up by the ringing relay Rr. Relays Tr controlled over the start circuit may connect up particular wipers or switches giving access only to the group containing the calling line. Third arrangement, Fig. 3 (not shown). The arrangement is similar to Fig. 1, but provides for tens and units grouping. The connecting relays of all subscribers having the same units digit are connected in parallel to one contact of switch V and the selection of the particular relay required is effected as regards the calling party by its line relay and as regards the called party by an additional tens switch. Fourth arrangement, Figs. 4, 5; local call. The operation of the relay chain Xr, Wr in response to impulses, whether produced automatically by contacts D3, Z3, when the chain acts as a call-finder or from a subscriber's dial represented by the interrupter I, is described with reference to Fig. 5. At the first connection of ground to contact Z1, relay Dr operates completing a circuit for the upper winding of Zr and a locking circuit for itself through the lower winding of Zr which is differential. At the next break, Zr operates and at the following make is held but Dr is short-circuited and releases. When ground is again removed, Zr also releases and the cycle is repeated, Zr operating at each odd impulse and releasing at each even impulse. At the first impulse, relay Xr operates ; at the second, Xr is locked in series with Yr; at the third, Ur operates; at the fourth, Ur locks in series with Vr which releases Xr, Yr; at the fifth, Wr operates and Vr holds ; at the sixth, Vr is released and Wr locked ; and at the seventh Xr operates again. The relays such as Abr 1, Fr, &c., shown in Figs. 4 and 5, with a thick line at one side are of the type which remains operated after energization until a further current pulse is received. When a call is initiated by a subscriber, common start relay Sr is operated to start the relay-chain operating as a finder, connecting one conductor of each line in turn to relay Mr. When the calling line is reached, Mr operates releasing relay Sr and completing a circuit for operating the appropriate connecting relay Abr1 .. Abr4. Relay Ar oper. ates over the calling line energizing Qr, and ground is connected to lead x to cause Mr to operate as a buzzer to generate dialling tone. After the relay chain has been set by impulses, ringing relay Rr operates, and ground is connected to lead y so that relay Mr acts to produce ringing tone, ring-back tone being also supplied to the calling subscriber over resistance R. The connecting relay of the called subscriber is then operated and talking current is fed to both parties in parallel over relay Ar. To call a party absent from his telephone, digit 5 is dialled operating Fr which lights a lamp L and connects the talking conductors of all lines to the link circuit 4 so that the subscriber wanted may speak by going to the nearest station. By using differently-coloured lamps and a plurality of relays Fr, a number of different subscribers may be thus called. If a subscriber wishes to operate an annunciator, he dials 6 to energize Gr and in a similar way by dialling 7, Hr may be operated to close a control circuit for a motor, radiator, &c. Main-exchange call. On an incoming call, a characteristic bell K<1> is rung and may be answered by any local party who after obtaining connection to the link 4 operates key 13 to unbalance relay Er which operates Ir to bridge the incoming conductors CL. If the call is for another subscriber, key 13 is again operated to release Er. A local connection is now set up to the wanted party who operates his key 13 to connect himself to the junction by energizing Er again. If a local call is taking place when a call comes in over the junction, relay Kr is operated and the ringing current is heard in the circuit 4 by induction through Er. An outgoing call is established in a similar way by operating key 13 and transmitting impulses which are repeated over the junction by Ar.