Patent GB-661163-A (GB)
Title: Improvements in or relating to switching devices for the setting of cross-bar switches by means of markers
IPC: H04Q3/00
Filed: 1947-05-19
Abstract: 661,163. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. May 19, 1947 [May 23, 1946], No. 13412/47. Class 40 (iv)] In a cross-bar system in which the marker controlling the operations of the switches is divided into units each concerned with only a single switching operation and in which only those units are taken into use at one time that are required for an interrelated series of operations, e.g. the connection of a calling line by way of an intermediate link to a register, means are provided for checking the operation of the switches and for changing the connection if a fault is found. Description is given of the connection from a calling line L, Fig. 2, over primary and secondary switches SA, SB to an intermediate link M and thence over primary and secondary switches RA, RB to an idle register. Ten lines served by switch SA1 have their line relays LR1-10 arranged so that only one can operate at a time. Each switch SA has a group relay, and the group relays GR1-10 are also arranged so that only one can operate at a time. On a call occurring, LR10, say, energizes and connects up group relay GR1 in series with MR1. The latter connects up AAG, Fig. 7, which associates the marker units PAO-8, PB1-8 of the SA, SB stages with the unit PC1-8 of the RA stage. Other switching operations within the exchange are initiated by MR2-5, and the circuits of MR1-5 are arranged so that operations that are liable to interfere with one another cannot occur at the same time. Energization of LR10, GR1 operates selecting magnet AS1, pertaining to the calling line, and SKR1. Each operating bar of SA1 is connected to a selecting bar in one of the switches SB, and the operating bars of these switches are connected over links M to the selecting bars of the switches RA, of which the operating bars are in turn connected to the selecting bars of the switches RB. The test circuits of the links M are connected in one direction over back contacts of the relevant bars in SA, SB, and in the other direction over front contacts of all relays such as AA1, which are energized by AAG and each of which is individual to a switch RA, back contacts of relays such as AB1 individual to switches RB and back contacts of the operating bars of the switches RA to d3. All the test circuits thus partly formed are completed by SKR1 over ten relays such as PA3, 5 in parallel, r8, r9 and wire d1, while wire d3 is connected over relays RV1-10 in parallel to idle registers. PA5, e.g., energizes in series with, e.g. RV1, and the operating magnet A1 corresponding to PA5 energizes in series with PA8. PA5 holds over PA6, which pulls up when A1 disconnects the test circuit. Selecting magnet BS1 energizes in series with PA7. BS1 connects up SL1 which con. nects operating magnets B1- 10 to front contacts of relays such as PB3, 5 in relay group PB similar to group PA, and which also completes the test circuits of links M1-10 over relays such as PB3, 5 in parallel, r13, r12 and d1. PB3, say, and PB6-8 pull up, and operating magnet B10 and selecting magnet MS10 follow. AB1 energizes, holds operated relays such as PA5, PB3, and connects relays such PC3, 5 in group PC over back contacts of N1-10 to d3. One of these operates and connects the corresponding operating magnet in series with PC7  and selecting magnet of RB1 in series with PC8. PC6 operates when N1, say, energizes. Operating magnet R1 of RB1 corresponding to RV1 energizes. Connection to the register is maintained by the several operating magnets over auxiliary windings. Busy and faulty conditions. If no idle operating bar is found in SA1 or if no idle register is available, PA1 energizes in place of one of PA3, 5 and causes busy signal to be given. Each relay such as PA3, 5 is associated with a relay such as PA2, 4. Operation of PA5, say, disconnects PA1 and makes a circuit for PA4 in series with FA, Fig. 8. If the connection is properly extended this circuit is broken by PA6-8. Otherwise PA4, FA pull up, marking relay PA5 is released and a fresh test is made. Cross-bar switches K1, K2 are provided for registering faults. PA4 connects up selecting magnet S20 in K1 corresponding to bar A1, while FA connects up selecting magnet S1 in K2 corresponding to switch SA1. Operating magnets BF1, 3 operate and so does one of F4-6 (dependent on PA6-8) to light a fault lamp L1-3. FA is released. On pressing a key T1 (which corresponds to the switching stage) lamps light to indicate the switch SA1 and the bar A1 as being faulty. If there is a fault in the switching stage SB, it is registered on bars BF2, 4 and is identified when key T2 is pressed. When the connection has been properly extended in the first switching stage SA, relays PA6-8 make a circuit for a very. slow-acting relay PB1. On an idle operating bar being found in SB1 this circuit is opened by PB3, 5. Should the selected bar be faulty, it is released by PB2, 4 and the circuit for PB1 is remade. If no idle bar can now be found in SB1, PB1 operates and connects up PAO, which, assuming PA5 is up, energizes PA4 to release it and so causes the selection of a fresh operating bar in SA1 and a different switch SB. In the same way relays PB6-8 make a circuit for a very slow-acting relay PC1 which operates when no idle and faultless operating bar is found in RA1 and connects up PAO. Rectifiers e1-20 and e31-30 prevent earth faults acting on the relay chains PA3, 5 and PB3, 5. Testing. If key PK is depressed the operation of PC7, 8 on the completion of a connection to a register connects up PAO to start a fresh connection. Thus the operating bars may be tested in succession and the faults indicated.