Patent GB-223985-A (GB)
Title: Improvements in or relating to automatic switching arrangements particularly for use in telephone systems
IPC: H04Q3/42
Filed: 1923-07-31
Abstract: 223,985. Barnay, A., July 31, 1923. Automatic exchange systems and apparatus.- A single-motion selector, controlled by one or more marking switches, is provided with a plurality of wiper sets, the wiper set having access to a wanted line or group of lines being connected up by switching means controlled over the marking apparatus. In the system described, a call is extended over an idle call-finder A, Fig. 2, permanently associated with a preliminary selector B, a group selector D having individual to it a marking switch C<1>, and a connector E, Fig. 3, controlled by permanently-associated tens and units marking switches C<2>, C<3>. Where several lines are allotted to a wanted number, a rotary connector F, Fig. 4, is taken into use the circuits of which are slightly different from those of the connector E, Fig. 3. All the switches are of the step-by-step type in which the wipers are advanced on the retraction of the stepping magnet. To decrease hunting time and increase switch capacity, the switches in the talking circuit are provided with two wiper-sets, the appropriate wiper-set being connected up by a switching relay controlled in the case of the call-finders and preliminary selectors over the test wipers, and in the group selectors and connectors over the marking switches. A modification is described in which the marking apparatus is associated with a group of group selectors or connectors, when the marking apparatus is taken into use by a group selector or connector, the remaining switches of the group being busied until the switch in operation has selected a wanted line and the marking apparatus has been restored. The number of trunks allotted to each group in the group selectors and ma.rked by the marking switches may be varied to suit tratlic requirements. The talking circuit switches mav be provided with more than two wiper sets, and the connectors with marking switches for receiving more than two digits. If the group selectors have two wiper sets (for odd and even groups respectively) and only one marking wiper, if all the contacts are to be utilized, an odd group must have allotted to it the same number of trunks as the even group above or below it, but if two marking wipers are provided, all the groups may be allotted different numbers of trunks. An example of this means of variable trunk grouping is described as applied to the interchange trunking in a multi-exchange system. Operation of first system, Figs. 2 and 3 : callfinder A and preliminary selector B. When a calling subscriber removes his receiver, his line relay 2, Fig. 2, is energized, puts a selectable potential (over the left-hand winding of the cutoff relay 5) on the test terminals in the callfinders serving the group, and grounds a common starting wire. A starting relay 33 of the first idle call-finder is thereby energized, earths the upper and lower test wipers 10, 13 through test relays 16, 24, and closes a circuit for the stepping magnet 50, which rotates both wipersets until one of them engages the calling line, when the corresponding test relay 16 or 24 is energized, opens the driving circuit, energizes a traffic meter, and connects up the appropriate wiper set. The cut-of relay 5 is also energized, disconnects the common starting wire and the line relay 2, and removes a shunt from its high resistance right-hand winding, thereby reducing the potential on the test lead to prevent other call-finders from stopping on this line. When the starting relay 33 was energized, a circuit was also closed for the driving magnet 57 of the associated preliminary selector B, and the test wiper 53 was connected to the upper low-resistance winding of a test relay 42. When a trunk to an idle group selector is engaged, the test relay 42 pulls up, connects its lower high-resistance winding to the test wiper 53 to mark the seized trunk non-selectable, opens the circuit of the starting relay 33, establishes a holding circuit for the relays 5 and 16 (or 24) at contact 44, and connects up the wipers 54, 55. The relay 33 relapses and extends the common starting wire to the next call-finder. If the preliminary selector B finds an idle trunk before the call-finder engages the calling line, the circuit of the relay 33 is opened at contact 45 but is immediately re-established over a circuit 46, 28, 19, which is opened on the subsequent response of a test relay 16 or 24. Group selector, Fig. 2. When the calling line is extended to the group selector, the line and slow-release relays 65, 68 are energized, and dialling tone is sent back from the transformer 109. The relay 68 places a holding ground on the test wire, and at contact 75 earths the inner contacts of the marking switch C', the odd contacts being earthed over the upper winding of a wiper switchover relay 90. The calling party now dials the first digit, the intermittent relapses of the line relay 65 closing the circuit of the stepping magnet 98 of the marking switch C'. which extends ground over one of its outer contacts and a marking wire to a group of odd and even marking contacts of the group selector. These contacts mark both an odd group accessible to the upper wiper set and an even group accessible to the lower wiper set, the appropriate wiper set being subsequently connected up as described below. A slowrelease relay 77 is energized in series with the marking switch stepping magnet 98. The marking wire 101 extending from the first and second outer marking contacts of the switch C<1> is connected to the marking contact of the group selector normally engaged by the wiper 125, so that when the marking switch wiper 100 is resting upon or passing over these contacts, a relay 84 is energized and at contact 89 opens the group selector driving circuit. If the first digit is 1 or 2, therefore, on the relapse of the series relay 77, a trunk-hunting operation takes place as described below, but if the first digit is greater than 2, directly the marking-switch wiper 100 leaves the second marking contact, the relay 84 relapses and completes a circuit 64, 106, 70, 89, 76, 83 for the group selector stepping magnet 115. The group selector wipers are now advanced during the further rotation of the marking switch, and when the wiper 125 arrives at the first marked contact, the relay 84 again energizes and opens the group selector stepping circuit. If the marking switch is set to an odd position the switchover relay 90 energizes in series in this circuit, locks up, and connects up the upper wiper set, but if the first digit is even the lower wiper set remains connected up. On the cessation of the impulse series, the relay 77 relapses, connects the test wiper 126 or 129 to ground over the lower winding of a test relay 61, and completes a circuit 64, 82, 88, 117, for the group selector stepping magnet 115, which rotates the wipers until the selected wiper set engages an idle trunk in the wanted group, on which the test relay 61 energizes, locks up over its upper winding, opens the stepping circuit, and extends the calling line to the selected trunk. If all the trunks in the wanted group are busy, the wipers are driven on to the first contacts of the next group, when, as the wiper 125 does not find ground, the relay 84 relapses and closes a restoring circuit 64, 106, 70, 89, 117 for the group selector. The calling subscriber receives a busy signal over the transformer 110, and when he hangs up, release takes place as described subsequently. When the group selector D is taken into use, a busy relay 118 is energized over the holding wire. If all the group selectors serving a group of preliminary selectors B are engaged, a chain circuit is closed for a relay 120, which energize the test relays 42 of all the idle preliminary selectors, thereby opening the circuits of their starting relays 33 and switching over the starting wires. Connector E, Fig. 3. The line relay 145 closes a circuit for the usual slow-release relay 153, which connects holding ground to the test-wire. energizes a change-over relay 161 over the wiper 207 of the tens marking switch C<2> in its normal position, and grounds the inner contacts of the units marking switch C<3> over the circuit 159, 186. The last-mentioned ground extends over the wiper 214 to the inner contacts of the tens marking switch C<2>, the grounding circuit to the odd contacts including the lower winding of a wiper switch-over relay 196. The calling party now dials the tens digit and impulses are sent over a circuit 182, 147, 148, 157, 170, 163, to the stepping magnet 205 of the tens marking switch C<2>. After the first impulse the circuit of the changeover relay 161 is transferred to contacts 164, 150, 186, 159. The marking wire extending from the first and second outer marking contacts of the tens switch C<2> is connected to a marking contact of the connector normally engaged by the wiper 224, so that when the tens switch wiper 207 is resting upon or passing over these contacts, a relay 177 is energized and opens the circuit of the connector stepping magnet 215. If the tens digit therefore is 1 or 2, no group hunting movement takes place, but if the tens digit is greater than 2, directly the wiper 207 leaves the second marking contact, the relay 177 relapses and completes a circuit 159, 186, 209, 179, for the connector stepping magnet 215. When the upper and lower wiper sets arrive at the first contact sets in the odd and even tens groups marked by the tens switch C<2>, the relay 177 again pulls up and opens the stepping circuit. If the tens switch is set to an odd digit, the wiper switch-over relay 196 energizes in series with the relay 177, locks up, and connects up the upper wiper set, but if the tens digit is even, the lower wiper set remains connected. On the relapse of the series relay 148 on the cessation of the tens impulses, the changeover relay 161 is de-energized and transfers the impulse circu