200,209. Conrad, H. S. April 8, 1922. Automatic exchange systems and selectors. - In a fluid-pressure operated switch, particularly suitable for use in automatic telephone exchange systems, the operating fluid is admitted to fluidoperated driving means in pulsations under the control of independently generated impulses. The invention is described as applied to a two-co-ordinate connector, the wipers 74 - - 77 of which are first stepping along in a horizontal direction by a pneumatic motor 25 and then stepped vertically upwards by a pneumatic motor 38. The stepping mechanism is so arranged that the wipers are moved a half step on the actuation of the motors and another half step on their relapse. Interruptions in the circuit of the line relay 3, produced by dialling impulses, intermittingly energize a relay 56 controlling a valve 58 to send air pulsations through the pipe 60 leading to the stepping motors 25, 38, through valves 64, 69 controlled by a side switch. The side switch 41 is operated by a slow-return pneumatic motor 46 which remains operated during the. trains of impulses and only relapses to rotate the side switch during the prolonged pause which ensues on the cessation of a series of impulses. During the transmission of impulses the line wipers 74, 75 are disconnected from the calling line 1, 2 at contacts 79, 80, 83, 84 by the actuation of the side-switch motor 46. Construction of switch. The wipers 74 - - 77 are mounted on a bar 27 sliding vertically on a cross-shaped plate 17, which in turn slides horizontallv on a cross-bar 16 of the framework 14, 15. The plate 17 is moved to the right by stepping pawls 21, 22 mounted on a lever 20 pivoted on the cross-bar 16 and actuated by the horizontal stepping motor 25, which is carried by the frame 14. The pawls 21, 2'2 are brought into operative relation with the ratchet teeth by a member 23 pivoted to an extension of the frame and actuated by a slow-return motor 11 through a bell crank 12 and rod 24. When the motor 25 is actuated the pawl 22 advances the slide 17 half a step, and on its relapse the lever 20 is returned by a spring 26 and the slide is advanced another half step. The bar 27 is stepped up vertically in a similar manner by the pawls 31, 32, mounted on a lever 29 pivoted on the plate 17, and actuated by the stepping motor 38 and spring 38<a>. The pawls 31, 32 are brought into operative relation with the ratchet by a member 33 pivoted to the plate 17 and actuated by a bell crank 36 connected to the rod 24 by a rod 35 and bell crank 34. The side switch consists of a pivoted toothed disc 39 stepped round by a pawl 48 when the motor 46 relapses and the lever 45 is returned by a spring 47. Normally a spring 41 holds the disc in the position shown against a pin 42. In this position an arm 68 of a bell crank 66 rests in a notch in the disc, and the valve 64 is held open to admit air pulsations to the horizontal motor 25. A holding pawl is actuated by the operation of the pawl motor 1.. When the disc 39 is moved to its second position the arm 68 is removed from the notch and the bell crank 66 turns on its pivot and permits the valve 64 to close. At the same time an arm 72 on a bell crank 71 drops into another notch on the disc and the valve 69 is opened and admits air pulsations to the vertical motor 38. On the sideswitch moving to its third position, both arms 68, 72 ride on the periphery of the disc and both valves 64, 69 close. Release is effected by the relapse of the motor 11 which withdraws all the pawls 21, 22, 31, 32, 43. A detent 100 is pivoted on the framework and is normally leld out of engagement with a third rack on the slide 17 by a pin 101 on the slide 27. When the slide 27 rises with the wipers, the pin 101 releases the detent 100, which engages its associated rack and thereby prevents horizontal release until the vertical release movement is completed and the slide 27 is in its normal position. The motors 11, 46 are rendered slow-to-return by the insertion of check valves 63, 62 in their inlet pipes. Operation of switch. When the switch is taken into use, the line relay 3 attracts its fast armature 5 and sluggish armature 4, thereby preparing a circuit for the impulse relay 56 at contacts 53, 54, and opening valve 7 to admit air to the local supply pipe 9. The pawl motor 11 is first actuated to bring all the holding pawls into operation, and the fast armature 5 then responds to the first series of impulses and at contacts 51, 52 intermittingly energizes the impulse relay 56, which controls the valve 58 to admit air pulsations to the horizontal stepping motor 25 and to the side-switch motor 46, which is maintained operated throughout the impulse train. The wipers 74 - - 77 are thus moved below a particular column of contacts. On the cessation of these impulses, the motor 46 relapses, the disc 39 is driven to its second position, and when the next series of impulses is transmitted the air pulsations pass through the valve 69 to the vertical motor 38, which in conjunction with the spring 38<a> steps up the wipers to the wanted contact set. At the termination of these impulses the motor 46, which was actuated throughout their transmission, again falls back and the disc 39 is moved to its third position in which both valves 64, 39 are closed. The calling line 1, 2 is now connected to the wanted line over springs 79, 80, 83, 84 and wipers 74, 75. When the calling party hangs up the relapse of the sluggish armature 4 closes the valve 7, the pawl motor 11 falls back, and all the holding pawls are released to enable the parts to restore to normal. According to a modification the pawl motor 11 is controlled by a valve which is opened when the valve 58 is closed and vice versa.