Patent GB-759756-A (GB)
Title: Interconnecting of subscribers' lines in final selectors
Inventor: OBERMAN ROELOF MAARTEN MARIE
IPC: H04Q3/42
Filed: 1952-10-17
Abstract: 759,756. Automatic exchange systems. STAATSBEDRIJF DER POSTERIJEN, TELEGRAFIE EN TELEFONIE. Oct. 17, 1952 [Oct. 27, 1951], No. 26128/52. Class 40 (4). Final selectors having normal outlets to one hundreds group also give access to overflow outlets from other hundreds groups. The register comprises a device, set in accordance with the digits designating the desired hundreds group, which tests whether there is a free final selector having normal outlets to the wanted group, and if not, the device is reset to a position indicating the hundreds selector containing the overflow outlets whereupon a further test for a free selector is made. The invention is described with reference to a 10,000-line exchange of the type described in Specification 750,130 in which only two selecting stages are used, the first selector being set in accordance with the first two digits and the second or final selector being set in accordance with the last two digits, a test being first made in the register-controller for a free final selector for the wanted hundreds group and the register then hunting for a free first selector having access to the free final selector. Two embodiments are described. In the first, each hundreds group is subdivided into groups of 20, the corresponding overflow groups being located in subsequent consecutive hundreds selectors as illustrated, the left-hand columns representing the normal outlets of the selectors and the right-hand columns the overflow outlets :- In the second embodiment the various into groups of 25 which are cyclically permuted hundreds are formed into closed groups of amongst the 5 selectors thus :- 5 hundreds groups and the overflow outlets In the first case the number of the hundreds selector in which the overflow outlets occur can be obtained by adding to the number of the hundreds group the number of the group of overflow outlets, e.g. the overflow outlets for group B60 are found in the selector B + 3 = E. Similar considerations apply in the second case but since the permutation is cyclic, after obtaining the sum, the remainder after division by 5 must be taken. Detailed description; First embodiment. The received digits are recorded in binary form on relay chains AA . . . AD (thousands) BA . . . BD (hundreds) CA . . . CD (tens) DA . . . DD (units). The thousands digit marks a " tens " contact of bank a of the busy testing switch BZ and with sequence switch SSU in position 1 switch BZ hunts for the marked contact until stopped by the test relay T. When the next digit is received contact a operates, followed by X and Y, the latter releasing X (which steps SSU to position 2) and T, whereupon Y releases and BZ hunts for the contact in the succeeding decade marked by the second digit and when this is found T operates and stops BZ. Relays X and Y operate and X releases again to step SSU to position 3. If the second digit is O, T reoperates over the contact-tree BA . . . BD with SSU in position 2, and brings up X and Y, Y releasing X to step SSU to position 3 and also releasing T. If there are free selectors giving access to normal outlets of the wanted hundreds group, P remains operated over bank b of BZ and busy contacts ek of the final selectors of the wanted hundreds group, and hunting for a free first selector having access to the wanted final selector is initiated as described in Specification 750,130. If, however, P releases BZ is again started and moves on to a contact marked by the contact-tree of relays FA . . . FD. These latter have been operated so as to represent in binary form the sum of the hundreds digit represented on relays BA . . . BD and the overflow group number which is represented on relays EA . . . EC, the latter having been operated over a contact-tree of CA . . . CD. Special arrangements are made in case the sum represented by FA . . . FD is a multiple of 10. In this case the marking is obtained over a second contact-tree of AA . . . AD whose outlets are staggered by one compared with the first contact-tree of that set. When BZ stops on its newly marked position T operates Q which permits relay S to test the final selectors having access to the required overflow outlets whereupon if one is available the register hunts for a first selector having access to the free final selector as before. If the overflow outlets are to be used, relay P will have released and the condition of this relay is therefore signalled over the first selector by means, not shown, to operate the wiper switching relay in the final selector. Second embodiment. In this case the switch BZ is replaced by a cross-bar switch whose cross-points when operated connect a test circuit similar to that of Fig. 1 to paralleled busy contacts of final selectors serving hundreds groups represented by the position of the crosspoints. The thousands digit, received on relays AA . . . AD operates one of the select magnets H1 . . . H10 and the second operates the hold magnets V1 . . . V10. If the test proves negative the cross-bar switch is released and a cyclic shift is applied to the outputs of the BA . . . BD chain by contacts of the chain C1 . . . C4, operated in accordance with the tens and units digits to indicate the number of the overflow group required. The cross-bar switch is then operated afresh to test the newly designated final selectors and the establishment of the connection proceeds as before. As an alternative to the chain C1 . . . C4 a rotary switch wired as shown in Fig. 3 and set in accordance with the overflow group number may be used.