Patent GB-990215-A (GB)
Title: Improvements in or relating to arrangements for scanning a set of apparatuses
IPC: H04Q3/00
Filed: 1963-05-03
Abstract: 990,215. Automatic exchange systems; circuits employing bi-stable magnetic elements. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. May 3, 1963 [May 8, 1962], No. 17595/63. Headings H3B and H4K. In an arrangement for scanning a group of equipments which are subdivided into at least three sub-groups and in which the equipments of each sub-group are scanned successively, the order in which the sub-groups are scanned is such that the equipment of at least two subgroups are scanned at different frequencies. Thus in an exchange system it may be necessary to test the condition of a number of impulse repeaters more frequently than that of a plurality of subscriber's lines and this may be achieved as shown in Fig. 1 by connecting the repeaters to leads 1 to 6 and the lines to the three groups of leads 7 to 15 of the scanning arrangement comprising pulse sources A, B, C, D. With this arrangement each of the leads 1 to 6 is scanned successively by source A, the pulse on lead 6 also passing through gate P to trigger source B which thereupon scans leads 7 to 9, a pulse on lead 9 re-triggering source A. The pulse on lead 1 then steps on ring counter G so that the succeeding pulse on lead 6 is passed via gate Q to trigger source C and thereby cause the equipment of group III to be scanned, following which source A is again triggered and so on. Thus the equipments of group I are scanned three times as frequently as those in groups II, III or IV. A somewhat simpler arrangement which replaces the three gates P, Q, R and counter G by two gates is described with reference to Fig. 2 (not shown), and more elaborate arrangements for dealing with a larger number of equipments are described with reference to Figs. 3-7 (not shown). In the circuit shown in Fig. 8, counters X and Y each produce pulses which together uniquely identify one of the leads in each of the groups, the counters also being arranged so that on pulsing the last lead of a group they " idle " until the identity of the first lead of the next group to be scanned is transmitted to them, whereafter they successively scan each lead in that group. The last lead of each group is provided with a number of magnetic cores which store in 2 out of n code the identity of the first lead of the next-but-one group to be read so that when the last lead of group I, say, is pulsed, this identity of the first lead of group I is transferred to a row of cores K or L, say K. A pulse is also passed to bi-stable circuit FF so that the contents of row L, which contains the identity of the first lead of the next group to be scanned, are read out and passed to circuits X, Y. When the last lead of this group is pulsed the identity of the first lead of the next-but-one group to be scanned is stored in row L and row K is read out so as to reset the counters to group I and so on. Means for interrupting the scanning of any group so as to allow any particular lead to be pulsed and then for continuing the scanning at the point where it was interrupted are described with reference to Figs. 9-18 (not shown).