529,049. Automatic exchange systems. ASSOCIATED ELECTRIC LABORATORIES, Inc. May 9, 1939, No. 13882. Convention date, June 20, 1938. [Class 40 (iv)] In a system employing finder-connector links, the switch mechanisms are similar to that described in Specification 529,048 and comprise a number of wiper units arranged side by side, one of which is selected for movement in two directions, the three selections being effected by means of three operating bars which are moved longitudinally under escapement control. A common operating magnet responds to three train of impulses, and a change-over magnet puts the three operating bars under its control in turn. The movement of the hundreds bar selects one of five wiper units and also operates contacts to control wiper-switching according as the hundreds digit is odd or even. Line finder, Fig. 17. Line relay 350 connects up start relay 390 of the allotter and closes tens and units marking circuits 330, 331. Relay 400 energizes, connects up 380 in the allotted finder and starts the switch 465, the magnet 479 of which interacts with 410 until the permanent hundreds marking is picked up, and relay 420 operates. The magnet M2a receives an impulse, bringing the escapement control mechanism into the first off-normal position. The switch 465 continues to move at a slower speed by the interaction of the magnet 479 with both 415 and 410 until a subnormal position is reached in which 420 is short-circuited. During the latter movement, 415 sends impulses to the magnet M1a to set the hundreds bar. The magnet M2a receives a second impulse to bring the escapement control mechanism into the' second off-normal position. The switch 465 picks up the tens and units markings in a similar way and impulses are sent to the magnet M1a to set the corresponding bars. Finally, the escapement control mechanism stands in the fourth off-normal position, in which springs 260a are closed, so that one or other of switching relays 360, 370 pulls up over odd or even springs 237a controlled by the hundreds bar. The switch 465 is now in a position in which springs 502 are closed, and relay 498 energizes. Ground fed back over the third wire 327 kicks off the allotter in search of the next idle finder, which is indicated by the open condition of off-normal contacts 245a. The relapse of line relay 350 when cut-off relay 340 operates disconnects 390, and the switch 465 rotates to normal. The seizure of an idle finder by an allotter starts any other allotter in engagement therewith in search of a fresh idle finder. Connector, Fig. 18. Line and release relays 520, 530 prepare an impulsing circuit for the magnet M1b in series with sluggish relay 540. The escapement control mechanism is different from that of the finder in that the magnet M2b requires no preliminary impulse to render the hundreds bar operable. The magnet M2b however receives an impulse for each digit by the operation and release of 560, which is dependent on 540, so that the hundreds, tens and units bars are successively set. Relay 600 is controlled over odd or even springs 237b of the hundreds bar. If the wanted line is busy, relay 570 energizes and sends back a busy signal. If the wanted line is idle, switching relay 590 energizes on the relapse of 540, 560. Ringing takes place in the usual manner, and ring cut-off relay 580 operates upon reply and connects up backbridge relay 550. Release. The relapse of line and release relays 520, 530 connects up the motor M3b over off-normal contacts 245b to restore the operating bars of the connector. At the same time, the magnet M2b operates to advance the escapement control mechanism to normal. The relapse of relay 380, which was held over the third wire 327, brings about the restoration of the finder in a similar way. P.B.X. hunting. An additional wiper 512 is associated with the set of wipers of the connector which have access to P.B.X. groups, the corresponding terminals 704 being strapped to the test terminals 703, except for the last line of the group which has its terminal 704 blank. If the first line is busy, relay 570 connects up 610 over wiper 512, and this relay interacts with the magnet M1b to hunt for an idle line, 560 being held meanwhile. Relay 610 fails to re-operate when an idle line is found, and in any case on the last line of the group, and further operations take place as described above.