Patent GB-141710-A (GB)
Abstract: 141,710. Turcat, L. March 6, 1919, [Convention date]. Automatic exchange systems; impulse-transmitters.-A circuit is closed over one line to energize a relay to disconnect the selector wipers from the calling line, and the selecting circuit is then closed over the other line with an earth return. When the selector comes to rest, a ring- ing-circuit may be completed at the calling station, either automatically or by the depression of a key. Construction of impulse-transmitter. A drum 30, Fig. 5, is turned by a knob 20 until the number or name of the wanted subscriber appears beneath an aperture in the casing; the receiver is then removed from its hook 10, thereby locking the drum 30 by the engagement of a lug 34 in one of the teeth 31, and permitting the rotation of a crank-handle 3 which winds up a spring 6. When the crank-handle has turned through just over 360 degrees, it is automatically released from the spring 6, which then drives the impulse-sending mechanism to an extent determined by the setting of the drum 30. A shaft 1, revolubly mounted in the walls of the casing, is rigidly connected to a hub 2 on which are slidably mounted an impulse wheel 21, a toothed wheel 17 geared to a fly-governor 40, and a disk 11 having a projection 12, which co-operates with a stop 33 on the drum 30. The hub 2 also carries two pivoted members 4, 5, Fig. 6, which co-operate with a member 36 and a pin 28 on the crank-handle 3. The operation is as follows. The drum 30 is turned by the knob 20 until the desired number shows through an aperture in the casing; the receiver is then removed, thereby locking the drum 30, freeing the crank-handle 3, and moving the core 9 (and the parts 11, 17, 21 carried thereby) to the left in Fig. 5, the projection 12 on the disk '11 moving into the path of travel of the stop 33. The crank 3 is rotated clockwise through 360 degrees, the pin 28, Figs. 5 and 6, acting on the member 5 rotating the hub 2, thus winding up the spring 6. When the crank and hub have turned through 360 degrees, the member 4 engages the member 36 and forces it against a stop 38, whereby the member 5 is moved out of the path of the pin 28, thus freeing the crank-handle 3, and releasing the spring 6 which rotates the hub 2 in the reverse direction. This movement of the hub 2 is conveyed by a pawl 19, Fig. 5, to the parts 11, 17, 21, which rotate until the projection 12 engages the stop 33 on the drum 30, the movement of the wheel 21 beneath the pawl 22 operating the impulse-sending springs 23 - - 27. When the subscriber replaces his receiver, the core 9 and parts 11, 17, 21 are moved to the right, thus allowing the spring 6 to complete the rotation of the impulse wheel 21 &c., whereby further impulses are sent to line to bring the selector to its initial position. Circuits. Each subscriber's line terminates at the exchange in a selector, the wipers of which normally engage contacts corresponding to that line. On the first movement of the pawl 22 into a tooth of the impulse wheel 21, Fig. 1, the earthed spring 23 engages spring 26, thereby earthing line 68 and energizing a relay 54, which disconnects line 69 from the wiper 64 and connects it to the line relay 58. On the further movement of the pawl 22 earthed spring 23 engages springs 26, 27, thereby earthing line 69 and energizing relay 58, which causes the magnet 61 to step the ratchet 63 one step. This action is repeated for each step of the wheel 21 until the arm 12 engages the stop 33, when a ringing-circuit is momentarily completed from grounded spring 23, springs 24, 25, arm 12, stop 33, relay 44, line 69, wipers 64, 64<1>, line 69<1>, contacts 15<1>, 16<1>, bell 72<1>, contacts 49<1>, 48<1>, line 68<1>, relay 54<1>, and battery 67 to earth. The relay 54<1> is not excited, but the relay 44 energizes and maintains the ringing-circuit until the called subscriber removes his receiver. The speaking circuit is then completed, the voice currents passing over the loop circuits 68, 69 and 68', 69<1>, which are joined through the condensers 78, 78<1>. The microphones 75, 75<1> are supplied with current over an earth return circuit including line 68 (or 68<1>), relay 54 (or 54'), and inductance 76 (or 76'). A low resistance coil 47 on the relay 44 gives a ringing- signal to the calling subscriber. The absence of such a signal indicates that the wanted line is busy. In a modified system, the supply of ring- ing-current is controlled by a push-button.