466,986. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. (Western Electric Co., Inc.) May 29, 1936, No. 15231. [Class 40 (iv)] In a cross-bar system, an inter-exchange call is set up, at the calling exchange, over non- numerical switches in tandem, a district frame and an office frame both comprising primary and secondary switches, and at the terminating exchange over incoming and final frames also comprising- primary and secondary switches. The trunking arrangements between the primary and secondary switches at each stage or " frame " are set out in the detailed description and include, in some cases, splitting the multiple of a horizontal bar to obtain a larger number of outlets. In the following abridgment a "district trunk " means a trunk incoming to a district frame and a "district frame link " means a link between primary and secondary switches thereat and so on for office, incoming, and final frames. The setting up of a connection is controlled by a registercontroller and translating marker at the originating exchange and by a register-marker at the terminating exchange. On initiation of a call, an idle district trunk and an idle registercontroller associable therewith over primary and secondary cross-bar switches, are connected up under the control of common apparatus, and the wanted number is registered. The register-controller seizes marker which receives the exchange digits and, after translation, marks a group of outgoing junctions. The marker finds an idle junction and makes a simultaneous test of available channels comprising district frame links, office trunks and office frame links, completing a connection over an idle channel, whereupon the marker transfers the remaining code digits and other information to the register-controller and releases. The other information may comprise zone indications and information for inserting line-compensating resistances, the use of which is not described in detail. The switches at a panel type tandem office and registers at a terminating cross-bar exchange are then set under revortive control. As the system is intended to work between panel as well as cross-bar exchanges, the 4-digit subscriber's number is transferred to the terminating exchange in 5- digit non-decimal form, and is there re-translated into a 4-digit number for a cross-bar exchange. Non-numerical switching arrangements, Figs. 14 and 15. A line-switch group comprises ten sub-groups of primary switches, the horizontal contact rows of the switches of a sub-group being connected in multiple to ten links connected respectively to corresponding vertical contact rows of ten secondarv switches. The vertical rows of the primary switches are associated with the subscribers' lines. For convenience, the above mentioned ten subgroups of primary switches will be referred to as horizontal groups and a set comprising a corresponding switch in each horizontal group will be termed a vertical group. A complete line switch group is controlled by a common circuit. When subscriber 1400 calls and line relay 1401 pulls up, horizontal group relay 1500 operates in series with.common relay 1406 and relay 1405 individual to the switch pulls up together with corresponding relays of other switches in the horizontal group. If another call appears in a different horizontal group the relays corresponding to 1405 cannot, operate. Relay 1412 common to the vertical group containing the switch associated with the calling line pulls up in series with 1429, disables the other vertical group relays 1413, 1414, and operates relays 1416, 1419 also common to the vertical group. Relay 1416 closes points in the circuits of the vertical magnets such as 1415 of switches in the vertical group to connect them to ten common vertical test relays 1423 .. 1425 to which ground has been connected by 1431 operated by 1406. The only circuit completed is that between subscriber's vertical magnet 1415 and test relay 1423 in which 1415 does not operate but 1423 locks over its lower winding in series with 1430 which releases 1431 to disconnect the operating windings of the test relays. In the case of simultaneous calls to the same switch, more than one test relay 1423 ... 1425 operates but only the one nearest the right holds since it opens the holding circuits of the others. Reverting now to the operation of horizontal group relay 1500, this was followed by relay 1513 belonging to the same group and which connected the right-hand windings of ten relays 1514 ... 1518 to the lower armatures of the ten vertical magnets such as 1433 (one in each secondary line-switch) corresponding to the ten links such as 1409 connecting the cabled horizontal primary group to the secondary switches. The completion of non-numerical switching will be described later. Selection of idle district trunk ; registercontroller connecting arrangements and further preparation of non-numerical switches. Each of the 10 district trunks, Fig. 17, outgoing from one secondary line switch appears in a vertical row of a primary register-controller selector 1800 and the horizontal links 1801 from a pair of such selectors are multipled together and to two vertical rows (one in each half) of a secondary register selector 1802 split in two so as to have access to 20 registers. Each pair of primary selectors is associated with a different secondary selector so that there are five secondary selectors for the full line switch group, the remaining inlets to the secondary selectors being similarly associated with four other line switch groups. The 100 district trunks from a line switch group are distributed over 5 district frames the remaining inlets of which come from other line switch groups. Five selector control circuits are provided of which one, Figs. 16, 18 and 19 is shown, and each circuit has five group circuits such as 1803-1806 corresponding to the five different line-switch groups which have access to it. Each control circuit has a start relay 1900 operated over the lower and four similar contacts of 1511 which together with 1510 was operated by 1406. The junction of relays 1804, 1805 and of similar relays of the other four sets are connected to back contacts of the 10 register group busy relays 1901 .. 1904, the corresponding armatures of pairs of which e.g. 1901, 1902 are connected to armatures of 10 vertical magnets e.g. 1809 of a secondary selector, ground. being connected to the 1804, 1805 relays by unoperated magnets. Relays 1805 and 1806 are connected in series to 10 resistances 1810 each connected over an unoperated armature of a vertical magnet 1811 of the primary selector and over unoperated armatures of district trunk switching relays 1706, 1707 to battery. Similarly 1803 and 1804 are connected over corresponding circuits in the other primary selector having access to the same links 1801 as selector 1800. It will thus be seen that circuits are made for 1805, 1806 and similarly for 1803, 1804 if there is an idle associated district trunk, an idle selector link such as 1801 and an idle register-controller in the group associated therewith. Assuming that two or more district trunks having access to primary' selector- 1800 are idle, current is supplied to 1805, 1806 over two or more resistances 1810 and marginal relay 1806 operates in addition to 1805. Relay 1806 connects battery to the right-hand winding of 1514 the other end of which is grounded at the vertical magnet 1433 of the secondary line switch. Similarly 1516 may be operated by 1803 and other relays of the set 1514 .. 1518 may be operated by relays corresponding to 1806, 1803 in the other selector control circuits. Relays 1514 .. 1518 control circuits of five relays 1528 .. 1530 but if more than one of 1514 .. 1518 operate only a preferred one of 1528 .. 1530 pulls up depending on which horizontal group relay 1500 .. 1503 is operated. In the present case, 1528 is preferred and at its upper armature opens a chain operating circuit for relays corresponding to 1528 in other line switch control circuits. 1528 also energizes the righthand winding of 1908 which is one of five relays 1908-1910 individual to line switch control circuits and of which only one can lock in series with 1909. If 1901 is an unoperated register-controller group busy relay, ground from armature of vertical magnet 1809 of the secondary selector is extended to the left-hand windings of 1514 .. 1518 and to 1508 which opens the right-hand windings of 1514 .. 1518 so that 1514 if operated will hold/there being no holding circuits for the other relays. Relay 1535 pulls up and releases 1511, 1510 so that start ground is removed from 1900 and start relays of other selector control circuits, relay 1900 being held locally and other start relays released. If there are no trunk groups with more than one idle trunk, relays 1803, 1806 do not operate but trunk groups with a single idle one operate relays 1804,1805 which also operated in the first case, but now slow-to-operate relay 1509 and slow release relay 1510 have time to change their condition so that 1522, 1525 pull up to place the right-hand windings of 1514 .. 1518 under the control of 1804, 1805 whereupon the trunk group to be used is determined as previously described. This arrangement gives preference to trunk groups with more than one idle trunk. Relays 1535, 1514 energize the horizontal magnet 1427 of the primary line switch and also send a ground signal to relay 2106 which is one of 10 relays 2106 .. 2109 individual to the trunk groups. When start relay 1900 was operated, 1600 and 1920 pulled up and 1921 followed due to operation of 1909 which held 1600. The start relay is now released by 1921 (its original circuit had previously been opened) and connects battery to the windings of 2106 .. 2109 whereby the one 2106 receiving the ground signal operates and connects 10 test relays 2100 .. 2103 to resistances 1810 at the primary