Patent GB-919160-A (GB)
Title: Improvements in or relating to circuit arrangements for the multiple utilisation of selecting arrangements in telecommuncations installations
IPC: H04Q3/00
Filed: 1959-03-26
Abstract: 919,160. Automatic exchange systems. SIEMENS & HALSKE A.G. March 26, 1959 [March 26, 1958], No. 10713/59. Class 40 (4). In an arrangement in which a calling line is selected and identified on a co-ordinate basis, two selectors being operated to indicate the coordinates of the calling line, the same selectors are also used for determination of the " state of operation " (e.g. free or busy) of a marker wanted line, the presence or absence of outputs from the selectors being used to determine said " state of operation." As shown, Fig. 2, subscribers' line circuits E 1  . . . E 6  are arranged in two groups of three. A particular subscriber is designated in co-ordinate manner by potential on either of k11, k12 and potential on one of the leads k21 . . . k23. The busy or calling condition of a subscriber E1 (say) is indicated by the operated condition of his contact r11. When one or more subscribers are in the calling condition the normally present potentials on the designating leads g11 g12 pass via the subscriber's contacts to one or more of the OR gates M11, M12 to the first selector W1, which selects one of the groups thus offered to it and emits the designation of the group as a potential on one only, say g11 of leads g11, g12. Simultaneously an enabling potential is applied to the selector W2 which thereupon receives one or more identification signals from the group marked by g11 via gates U21 . . . U23 which are opened by enabling potentials on k21 . . . k23 during an identification operation. Selector W2 then makes a selection from these markings and emits a marking on one of leads l21 . . .23 indicative of the selection. In the case of a simple busy test of a subscriber, potential is first applied to lead vf to inhibit the normally present markings on g11 g12 and potentials are applied to one of leads k11 k12 indicating the group to which the subscriber belongs, and to one of leads k21 ... k23 indicative of the position of the subscriber within the group. Selectors W 1 , W 2  operate in succession as before to produce outputs on one of leads g 11 , g 12  and one of leads l21 ... l23 if the subscriber is free. No such output appears if the subscriber is busy. In the event of the subscriber being the first of a P.B.X. group, all such subscribers are arranged to be in a group indicated by a k terminal such as k 11  and arrangements are provided as described below to mark the appropriate ones of terminals k21 . . . k23 indicative of the other lines of the P.B.X. group. Fig. 4 illustrates the selectors W1, W2 in more detail. Bi-stable circuits Q1, Q2 are normally operative, the former providing the output potential normally present on leads g11, g12. The latter does not enable gates U1, U2 at this stage. For identification, an initiation signal is applied over lead a1 to circuit 1WI which stores the signals offered to it on its input leads and selects one, whose identity is indicated on one of leads 1g11, 1g12. When selection has been effected the selector emits a potential to OR-gate M3 whose output after a short delay changes over bi-stable circuit Q 1 to remove the normally present potential on both leads g11, g12. The potentials on the inputs to selector W2 are thus removed so permitting NOT gate S to change over bi-stable circuit Q2. This enables gates U1, U2 so that the selection present on leads 1g11 or 1g12 can now pass out to g11 or g12. Selections from the selected group are now offered to selector W2 which is now enabled over lead c1 by Q2 and the selector operates in a similar manner to W1 to emit the result on leads l21 . . . 123. Restoration of the circuit is then effected by potential on lead vi which restores the bi-stable circuits Q1, Q2. In the case of " state of operation " testing, a momentary interruption of the marking on a terminal such as k11 is effected (by means not shown) when the selector 1W1 operates, in order that Q2 may change over as described above. PBX working.-Fig. 3 illustrates circuits used in conjunction with those of Figs. 2 and 4 for busy testing of PBX subscribers. Each subscriber's line is associated with one terminal from each of groups 1k21 . . . 26 and k11 . . . 16. These sets of terminals may themselves be marked in co-ordinate fashion e.g. by a combination of markings in terminal groups k221 . . . k223 and k211, k212. One PBX group consists of lines associated with terminal k 11 in combination with terminals 1k23, 1k24, 1k25, the first named being the first line of the PBX group. Marking of terminals k11 and 1k23 opens gates 1P24, 1P25 which marks terminals k24, k25 as well as k23 which is marked directly. These markings enable the appropriate AND gates in the inputs to the selector W2, Fig. 2. Testing for different categories of busyness.- Successive tests may be made to determine whether a subscriber tests busy because he is about to initiate a call, or is engaged in a local call, or is engaged in a trunk call. Thus a subscriber's line circuit E, Fig. 5, may comprise three relay contacts r1, r2, r3 of which none are operated if the line is free; r1 and r2 are operated if a subscriber is just initiating a call; r 3  is operated if the subscriber is local busy and all are operated if the subscriber is trunk busy. In this case the successive tests may be effected by operating contacts h1 . . . h4 in their respective leads to the subscriber's line circuits. The arrangements may be used in systems possibly of the electronic type in which the calling and called subscribers are first identified and then a search is made for a free path interconnecting them.