631,883. Automatic exchange systems. AUTOMATIC ELECTRIC LABORATORIES, Inc. Nov. 21, 1946, No. 34589. Convention date, Nov. 21, 1945. [Class 40 (iv)] In a cross-bar system the operating magnets of a switch are operated sequentially in response to an incoming train of impulses, and are operated sequentially a second time, either automatically or in response to a second impulse train. The switch employed which is shown schematically in Figs. 5, 6 is that disclosed in Specification 628,402, and has a single group of operating magnets the first operation of which selects a row of contact sets, whereas the second operation selects a particular one of the sets in the previously selected row. Selector (Figs. 1, 5, 6). The conductors C116-C119 entering the left of Fig. 1 connect with the corresponding conductors of a line finder (not shown), the fourth conductor C119 being provided to control a special service or a restriction of service, in the succeeding switch train when the finder is associated with certain lines. In such cases conductor C119 is grounded. Group selection. When the finder is operated, it extends a loop over C116, C117 to operate impulse relay 180, followed by 160 which grounds C118 to hold the finder, and brings up dialling relay 110 which substitutes ground through a dial tone transformer (not shown) for direct ground on the lower winding of 180. The finder then extends the calling line to 180 and the caller dials the first digit, to which 180 responds. On the first release of 180, a ground impulse is extended to 110 (lower winding), and also over C508 to operate selecting magnet M1, Fig. 5. Re-operating of relay 180 to the second impulse brings up 140 in series with M1, thus transferring the impulsing circuit to M2 over C512. On the second release of 180, M2 is energized and when 180 again operates 145 comes up in series with M2, releases M1 and 140, and transfers the impulsing circuit to M3 over C513. Magnet M3 operates on the third release of 180, and is subsequently held in series with 150, when 180 re-operates. The operation of 150 releases M2 and 145 and transfers the impulsing circuit to M4 over C514. Subsequent impulses operate M4, M5, M6, M7 ... respectively, which hold in series with 140, 145, 150, 140 ... respectively. Relays 160 and 110 are slow-to-release and hold during impulsing. Assuming the first digit dialled is " 9 " M9 will be operated, and held in series with 150 after the ninth re-operation of 180. On the relapse of dialling relay 110 dial tone is disconnected and relay 130 comes up, followed by the control magnet CM and relay 120 in parallel. (The contacts of relay 120 are preferably operated by magnet CM.) The operation of CM causes the finger F9 (Fig. 6) previously operated by M9 to engage the rank selecting bar RS9 and shift it so that its associated contact operating members fall into slots in corresponding ones of the file selecting bars, such as FS1 ; while that of relay 120 releases M9 and relay 150. The finger F9 holds RS9 operated independently of M9, and relapse of 150 brings up 155 in series with 130. Hunting in the selected group. The operation of relay 155 extends ground over C515 to a chain of d contacts of the magnets M0, M9 ... M2 to M1. Operation of M1 extends ground over C516 to the b contacts of magnets M0, M9 ... M2 and over contacts M1b to M2, and also operates file selecting bar FS1 so that the contact operating member K91 presses its contact set 91 into engagement with the set of multiple conductors adjacent thereto. Each set of four multiple conductors extends to a corresponding connector, (Figs. 2-6), over conductors such as C201-C204, (Fig. 2), or alternatively to a second selector, (Figs. 1, 5, 6). The control lead C204 of the first connector in the selected 900 group will extend either ground or resistance battery, according as it is busy or idle respectively, over contact set 91 and C507 to relay 185. If it is busy, 185 remains down and M2 operates, releases M1, extends ground over C516 to M3, disconnects contact set 91 from C507, and operates FS2 and contact set 92. If, however, the second connector thus associated is idle, 185 comes up, followed by 190, and opens the circuit to M3 before that magnet has time to operate (M1 will have restored by this time). Operation of 190 transfers the calling line from relay 180 to relay 200, (Fig. 2), extends the fourth conductor C119 to C203, (Fig. 2), and extends ground over C507 to C204 to busy the connector. It also disconnects magnet CM and relays 120 and 160. To prevent momentary connections between successively numbered lines being caused during hunting by the simultaneous operation of adjacent magnets, separate conductors are multipled to the odd and even contact sets and these are connected together only when relay 190 is operated at the end of the hunting period. The restoration of CM rotates the shaft 600 of the latching mechanism to hold FS2 independently of M2. Relays 120, 180, and 185 restore, followed by 160 which disconnects relays 130 and 155 and magnet M2. Relay 190 alone remains operated. Release of selector. At the end of the call the loop circuit to the connector is opened, whereupon the release of the connector removes the ground extended over C507 from C204. Relay 190 relapses, and energizes release magnet RM over C519, which in turn releases the latching mechanism. FS2 restores and contact set 92 is opened. Contacts 601 are opened when the latching mechanism has restored. All trunks busy. If all the connectors accessible over contact sets 91 to 90 are busy magnets Ml to M0 will be operated sequentially and MO connects up relay 170 over C517 at the same time as it extends the connector control conductor to relay 185. Relay 170 is slower to operate than 185 so that if the connector is idle operation of 185 disables 170, but if it is busy 170 comes up and connects up busy tone over the lower winding of relay 180, and disconnects 185, CM, and 120. When the caller hangs up, 180 falls away followed by 160 which releases the preceding finder switch, relays 130, 155, 170 and magnet M0, and energizes RM to restore the selector to normal. Operation of connector, (Figs. 2-6) : Selection of ringing code group. When the connector is seized by a selector, or by a finder, the calling line is extended to relay 200, (Fig. 2). In the former case the connection to the dial tone transformer (not shown) over contacts of relays 310 and 460 is replaced by direct ground on the lower winding of relay 200. Operation of 200 brings up 210 which busies the connector. The first digit received which may either be " 2 or " 3 " controls the selection of the ringing code group. When relay 200 restores to the first impulse, M1 and relay 440 are energized in parallel, and when relay 200 re-operates at the end of the impulse 470 comes up in series with M1 and transfers the impulsing circuit to M2. The magnets and relays 470, 480, 490 operate sequentially in a similar manner to that described for the selector. Relays 210 and 440 remain up during impulsing. At the end of the train 440 restores, and extends ground over C528, contacts M2h or M3h, C527, C526, and either contacts M2g and C524 to relay 320 ; or contacts M3g and C523 to relay 330 dependent on the digit received. Assuming this to be " 2 " operation of 320 brings up 400 thus releasing M2 and 480, whereupon 310 operates in series with 320, releases 400, and prepares a circuit for the operation of 340 at the end of the next digit. " Tens " group selection. The next digit results in sequential operation of the magnets M to MO as before, and when relay 440 restores, relay 340 comes up over C528 and C527, and brings up relay 400 and magnet CM. Magnet CM causes the rank selecting bar corresponding to the operated selecting magnet, say RS0, to be operated. Operation of 400 releases MO and 470, whereupon 350 operates in series with 340, releases 400 and prepares for operation of 360 at the end of the next digit. " Units " selection. After sequential operation of the magnets in response to the next digit (accompanied by the operation of the corresponding file selecting bars FS1 to FS0 since RS0 is held operated), the restoration of 440 connects the control conductor of the called line through the last operated contact set (say 03) over contacts of the unoperated magnets, and C507 to relay 370, and extends ground over C528, C527 to relay 360. Relay 360 is slow to operate so that if the called line is busy ground on its control conductor will bring up 370 before 360 can operate and thus connect busy tone via condenser 203 to the calling line. When 360 operates it releases CM and brings up 400. Restoration of CM rotates shaft 600 to hold FS3 independently of M3, and operation of 400 releases 490 and M3. Relay 380 thereupon comes up in series with 360, connects the conductors C501 and C503 multipled to odd-numbered sets 01, 03... to C502 and C504 of the even-numbered sets, and transfers C507 from relay 370 to ground over relay 250. If the called line is busy 250 is disconnected at contacts of 370, but if it is idle, battery from the cut-off relay is extended over C507 and operates 250. Relay 260 follows, extends the calling line to relay 220, and releases 250 by short-circuit. Release when called line is busy. When the caller hangs up in response to the busy signal, 200 restores followed by 210 which initiates release of the switch train. Code ringing. If the called line is idle the calling party dials a further digit to select the ringing code in the previously selected group. The magnets M1 to MO are operated as before. Contact set 03 remains operated but does not interfere with the operation of the.magnets. Relapse of 440 brings up 420 which opens the impulsing circuit and connects together conductors C529 and C530 which had previously been separated to prevent momentary connections between conductors C531-C540 during sequential opera