Patent GB-202618-A (GB)
Abstract: 202,618. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Stehlik, R. F.). Aug. 17, 1922, [Convention date]. Automatic exchange systems.-In an impulse circuit, on the first response of the line relay the release or holding relay locks up in series with the switch driving magnet, which operates each time the release relay is short-circuited by the relapses of the line relay due to the dialling impulses. The shunting of the winding of the release relay has a retarding effect which makes it slow to release, thereby causing its armature to be held during the transmission of the impulses and rendering its relapse dependent upon the continued de-energization of the line relay. When the arrangement is applied to a numerical switch, the release relay and the usual series relay are both quick-acting and are connected in series with the driving magnet whch responds each time the highresistance release relay is shunted. The series relay, which is short-circuited over the working contact and armature of the line relay, responds on the first de-energization of the latter relay and is afterwards shunted each time this relay pulls up, but on account of the retarding effect of its shunted winding it only relapses on the continued energization of the line relay following the cessation of the impulse series. Bv this arrangement, both the release relay and the series relay are maintained energized independently of the line relay when the armature of the latter relay is not in engagement with either its working or its resting contact. The invention is described as applied to a system in which the line of a calling subscriber A, Fig. 1, is extended to a wanted subscriber A<1>, Fig. 2, over a line switch C, a first selector E, a repeater R, second and third selectors F, G, and a connector H. Means are provided whereby if either party omits to replace his receiver on the completion of conversation, after a predeterminel interval a. pilot lamp is illuminated at the exchange and a circuit is closed for an attendant's alarm buzzer. First selector E, Fig. 1. When the subscriber A lifts down his receiver, the line switch C connects his line to an idle selector E in known manner, energizing the line relay 35 which closes a series circuit for the release relay 36 and the vertical magnet 40. The release relay 36 locks up in series with the series relay 37 and the magnet 40. The series relay 37 and the vertical magnet 40 both fail to respond at this time, the former since it is short-circuited over the armature 46 of the line relay, and the latter on account of the high resistance of the release relay 36. When the line relay relapses in response to the first dialling impulse, on the engagement of the armature 46 with its resting contact, the release relay 36 is shortcircuited and the series relay 37 and vertical magnet 40 pull up. The magnet 40 raises the selector wipers a step and the relay 37 closes a circuit over the off-normal contacts 44 for the stepping magnet 38 which locks up over its armature 50 and prepares the circuit of the rotary magnet 42. The release relay 36 is prevented from falling back during the de-energization of the line relay by the retarding effect of its shunted winding. On the circuit of the line relay being again completed and its armature attracted, the shunt is removed from the relav 36 and the vertical magnet 40 de-energizes. When the armature 46 again engages its working contact, the series relay 37 is short-circuited, but it remains held during the transmission of impulses in consequence of the retarding effect of its shunted winding. The adjustment and turns on the relay 37 are such that it will not hold up indefinitely in series with the relay 36, in order that if the armature 46 does not touch its working contact during impulse transmission, the relay 37 still functions correctly. This cycle of operations is repeated for each impulse, the relays 36, 37 being alternately shunted by the de-energization and energization of the line relay 35. On the cessation of the impulse series, the shunted series relay 37 falls away and completes the circuit of the rotary magnet 42 which interacts in known manner with the stepping relay 38 to rotate the selector to an idle set of terminals in the selected level, the switching relay 39 then being energized. This relay disconnects the line relay 35 which shortcircuits the release relay 36, but the vertical magnet does not energize at this time since its circuit is open at armature 54. Repeater R, Fig. 1. The response of the line relay 68 closes a circuit for the release relay 69 in series with the resistance 92. The release relay 69 energizes the lower winding of a polarized relay 71 at armature 78.and closes a bridge across the two-wire trunk 86, 87 over a circuit including armatures 76, 80, the upper winding of the polarized relay 71, and the right-hand winding of the impedance 72, thereby, energizing the line and release relays at the second selector F, Fig. 2. The relay 71 does not respond at this time, the currents in its two windings being in opposition. The telease relay 69 also grounds the holding wire 65 since by this time the release relay 36 has fallen away and removed holding ground at armature 47. On the calling subscriber dialling the second digit. the line relay 68 intermittently de-energizes and opens at its armature 85 the bridge across the conductors 86. 87, whereupon the wipers of the selector F are raised to the desired level. At each relapse of the line relay 68, the release relay 69 is shunted, but its armatures do not fall away during the impulses on account of the retarding effect of its short-circuited winding. On the first relapse of the armature 84, a shunt is removed from a relay 70, which remains held during the impulse train and closes a more direct bridge across the conductors 86, 87 at armature 80, in the mid-position of which the bridge is held over a resistance 91. On the cessation of these impulses, the relay 70 relapses and restores the original bridge. The wipers of the selector F now rotate in well-known manner and engage an idle trunk to a third selector G which is operated in a similar manner by the third series of impulses to select a desired level, after which an idle trunk to a connector H is engaged. Connector H, Fig. 2. The line relay 105 closes a series circuit for the release relay 106 and vertical magnet 160, but the magnet 160 does not respond owing to the high resistance of the relay 106. The release relay grounds the holding wire 102 at armature 118 and locks up in series with the magnet 160 and series relay 107 over the normally closed springs 150 and armature 119, but neither the relay 107 nor the magnet 160 pull up in this circuit. The calling party now dials the fourth digit, interrupting the circuit of the line relay 105, and the release and series relays 106, 107 are alternately shunted and cause the vertical magnet 160 to raise the connector wipers to the desired level, in the manner already described with reference to the corresponding relays of the first selector E. After the connector wipers have moved out of their normal position, the series circuit for the relays 106, 107 and the magnet 160 is transferred over armature 119, off-normal springs 151 and armature 121. In the interval following the fourth impulse series the shunted relay 107 relapses and closes a series operating circuit for the release relay 106 and the rotary magnet 162, this magnet, however, remaining inert owing to the high resistance of the relay 106. A parallel circuit also completed for the relay 110 and vertical magnet 160, but these also do not respond on the same account. Interruptions in the circuit of the line relay 105 on the dialling of the fifth digit short-circuit the release relay 106 and cause the rotary magnet 162 to step the wipers on to the wanted line. Busy test, busy signal and busy release. The relay 110 responds when the release relay 106 is shunted at the first impulse, and remains energized during the rotary movement, and for a short interval afterwards, on account of the retarding effect of its winding, which is short-circuited when the line relay 105 is energized. The relay 110 connects the test wiper 142 to the busy relay 109, which, if the wanted line is engaged, pulls up, and on the relapse of the relay 110 an instant later locks energized over the release conductor 102 and connects busy tone to the lower talking conductor at armature 130. The calling party then hangs up and the connection is released. Ringing current. If the wanted line is idle, the busy relay 104 is not energized, and on the relapse of the relay 110 a circuit 118, 127, 111, 132, 142, 147, 148 is closed for the upper winding of the switching relay 111, which locks up over its lower winding, grounds the test-wiper 142, starts the ringing machine in operation by grounding the ringing machine lead at armature 139, and completes the ringing circuit at armatures 134, 140. A small condenser 128 bridged across the armature, 122 of the ring cut-off relay 108 allows enough ringing current to leak back to give the calling party an audible signal. On the response of the called party, the ring cut-off relay 108 is energized and locks up over armature 124, disconnecting ringing current, extending the test wire 102 to the test wiper 142 over armature 123, and connectng the called line to the backbridge relay 104 at armatures 122, 126. Talking circuit. The back-bridge relay 104 closes at armature 116 a locking circuit for the relays 108, 111 independent of the release relay 106, and reverses the current in the loop extending back to the repeater R, causing the response of the polarized relay 71, which extends the connection over armatures 81, 83 and energizes a reversing relay 67. The reversing relay 67 effects a current reversal over the calling loop for metering or oth