Patent GB-750130-A (GB)
Title: Trunking diagram for an automatic signalling system
Inventor: OBERMAN ROELOF MAARTEN MARIE
IPC: H04Q1/18
Filed: 1952-05-09
Abstract: 750,130. Automatic exchange systems. STAATSBEDRIJF DER POSTERIJEN, TELEGRAFIE EN TELEFONIE. May 9, 1952 [May 19, 1951], No. 11852/52. Class 40 (4). In a 10,000 line exchange in which a feedbridge VBC, Fig. 6, obtains access to a calling and a called line over two hundred point switches OZ1, OZ2 and BK, EF respectively, a calling line seizes a first line-finder OZ1 having access to a free feed-bridge and a free register; a free register is then seized and operates a finder LZ to connect it to the seized line-finder OZ1; the register then sets a switch BZ in accordance with the first two digits of the wanted line and receives busy or idle indications from all the final selectors EK having access to the group containing the wanted line; the register then operates a feed-bridge finder KZ to seize a feed-bridge VBC having access to a free switch EK having access to the wanted line; the first selector BK is then set to the wanted final selector and the second line-finder OZ2 set to the seized first line-finder OZ1; and the final selector EK is then set to complete the connection. The final selector and first line-finder may be the same switch. Trunking arrangements, Fig. 6. As shown a 10,000 line exchange comprises first and second line-finders OZ1, OZ2 and first and final selectors BK, EK, the settings of switches OZ2, BK determining the thousands and hundreds digits and the settings of switches OZ1, EK determining the tens and units digits of the calling and called lines respectively. 8 line-finders and 8 final selectors are provided per 100 subscribers lines. Each first line-finder of a 100- line group is multiplied to 64 second line-finder banks OZ2, there being 8 groups of 64 second line-finder/first selector links which contain the feed-bridges VBC. Similar arrangements apply on the selector side of the feed-bridges. The groups of 64 second line-finders and of first selectors are each divided into 8 sub-groups of 8, each second line-finder sub-group being crossconnected via the feed-bridges to a different sub-group of first selectors. 8 groups of 8 register-controllers REG are provided, one group for each of the 8 line-finders per 100 subscribers, access being obtained by a register to a line-finder of a particular hundreds group over a 100 outlet finder switch LZ. Each register contains a busy test switch BZ having 8 wipers, one for each of the 8 final selectors per 100 subscribers, and when the switch is set in accordance with the first two digits it receives indications as to the busy or idle condition of all 8 selectors having access to the wanted hundreds group. The switch KZ then hunts for a free feed-bridge circuit having access to a wanted final selector which is free (as tested over BZ) and hence the complete route through the exchange is determined. Allotting of first line-finder and register. Each group of 100 subscribers has a circuit, Figs. 7 and 8, containing 8 relays L (101 ... 108) each associated with a line-finder. When a calling condition exists in this 100's group the potential of the d-wire is lowered to operate relay OD1, Fig. 7. This operates the first L relay of the chain for which the associated contacts ob, b and vr are unoperated. Each ob contact becomes operated when the associated line-finder is busy. Each b contact becomes operated either if all the registers accessible to the line-finder are busy, or if all the feed-bridge circuits accessible to it are busy. The vr contacts are controlled by a " reservation " circuit, Fig. 9, and are operated if the number of feedbridge circuits, accessible from the finder, which are busy or which are about to be busied by a " calling " register controller is greater than a certain proportion of the total. Thus each group of 64 feed-bridge circuits is provided with a trigger valve such as B4, B5, Fig. 9, which operates relay VR1 when the left-hand grid becomes more positive than the reference potential of the right-hand grid as determined by resistors R91, R92. The potential of the left-hand grid is determined by the number of resistors R11 ... R18 switched in by rb contacts of the associated registers and the number of resistors R101 ... R164 switched in by kb contacts of the associated feed-bridge circuits. The rb contacts are operated when a register is in use and the kb contacts when a feed-bridge circuit is in use. Thus the busying of a feedbridge or the taking into use of a register which will subsequently seize a feed-bridge, raises the potential of the left-hand grid of B4, B5. The trigger valve B4, B5 is so biased on its righthand grid that in the first instance it changes over to operate VB1 when only a certain proportion of the group of 64 feed-bridge circuits have been seized or "reserved." Relay VR1 then renders this group unavailable until this proportion has been reached in all the feedbridge groups whereupon trigger valve B11, B12 operates relay CR1 which changes the bias on all valves like B5 to render available a higher proportion of feed-bridge circuits per group. When this proportion has been taken up in all groups valve B13, B14 operates CR2 to raise the permitted proportion still further. An equitable distribution of traffic over the feed-bridge groups is thus obtained. A further circuit of this nature, Fig. 10, is provided to operate a BR relay per group when all the feed-bridges in the group are seized or reserved. These BR relays operate corresponding B relays whose contacts occur in the chain of Fig. 8. These B relays are also operated over corresponding chains of register busy relays if all the registers of the group are busy. Seizure of register, operation of first linefinder and setting of register. The L relay operated in the chain of Fig. 8 designates the line-finder to be used. One line-finder per hundred subscribers may seize any one of the eight registers forming a group and this is effected over chain circuits like those at the bottom left of Fig. 10 in which the appropriate set of 100 l contacts (of which only a few are shown) are distributed in an even manner over a chain including register busy contacts rb to effect the operation of the seizing relay RS of a free register of the group. Relay RS brings up RA, Fig. 11<1>, which connects up a voltage comparator NW and starts the finder LZ. The L relay has applied a calling potential to the ebank of LZ and the sequence switch SS-A in its zero position applies a corresponding reference potential to NW. When LZ finds this potential NW operates to stop the switch and bring up H which allows RBB to operate in series with RA. Comparator NW is thereupon released followed by H which steps the sequence switch SS-A to position 1. This causes a reference potential characteristic of a calling subscriber's line to be applied to NW. Relay OA1 also operates in the first line-finder circuit to energize the finder drive magnet OD1. When the finder reaches the calling line a test circuit over the d-wiper of OZ1 and the b-wiper of LZ is closed to operate NW which stops the switch. Relay H operates followed by switching relay OB1 in the finder. NW releases, followed by H which steps SS-A to position 2. Impulse relay IR operates to the calling subscriber's loop and responds to dialled digits to set the digit switches MS1 . . . MS4, the sequence switch being moved successively to positions 3 . . . 6 under control of the dialling relay RC. Choice of feed-bridge circuit and setting of selectors. When sequence switch SS-A reaches position 3 after the reception of the first dialled digit, sequence switch SS-B goes to position 1 to start switch BZ hunting in search of a position marked by MS1 on its b-bank. When this is found T operates to stop the switch and bring up relay BR which moves sequence switch SS-B to position 2 provided SS-A has.reached 4, i.e. the second dialled digit has been received. If the second digit is not zero T then releases, switch BZ starts again until stopped by T which operates over the b-bank of MS2 and releases BR. If the second digit is zero T is not released when SS-B steps, BZ stays where it is, and BR releases directly. Release of BR sends SS-B to position 3 wherein A operates to start the feed-bridge finder KZ. The busy contacts of the eight final selectors serving a given hundreds group are multipled respectively to appropriate positions in the eight banks of the switches BZ whose wipers are connected to corresponding positions in the i-bank of -the feed-bridge finder KZ. This finder then rotates until stopped by the operation of the D.C. test device GT over the f-wiper of KZ, a busy contact of the feed-bridge, the c- and i-wipers of KZ, one of the wipers of BZ (say a) and a busy contact of a final selector. A free feed-bridge circuit having access to a suitable free final selector has now been found. GT operates H2 which brings up B and K. The latter releases GT and H2 follows to bring up BA in the first selector, and to step SS-B to position 4. A reference potential characteristic of the thousand digit is now connected to the comparison device NW1 and the first selector BK is caused to hunt until this potential is reverted over the e-wipers of BK, KZ, when NW1 operates and stops the switch. H2 operates, followed by L, which releases H to step SS-B to position 5 and L releases again. A hundreds digit reference potential is now applied to NW2 and DBK hunts again (if the hundreds digit is not zero) and NW1 again operates to stop the switch. H2 then operates, followed by BB. If the hundreds digit is zero NW1 fails to release, causing H2 to operate when L releases. Relay H2 opens the d-wire to allow BB to operate in series with BA and switch through. NW1 releases, followed by H2 which steps SS-B to position 6. The setting of the final selector takes place in a similar manner SS-B finishing up in position 8. When SS-B reaches position 4, OA2 operates in the second linefinder to energize the finder m