Patent GB-375380-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1931-03-20
Abstract: 375,380. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, Liverpool, DEYES, H. S., Springfield, Bridle Path, Eastham, Wirral, Cheshire, CORNER, A. C., 26, Pinfold Road, Streatham, London, and BEALE, C. E., 59, Towers Road, Wavertree, Liverpool. March 20, 1931, No. 8652. [Class 40 (iv).] In a system employing rotary connecting switches controlled as to the tens digit by markers and as to the units digit directly, ringing current is applied to one or other leg of party lines in accordance with the setting of the marker by the tens digit. In cases where the marker acts also as a discriminator and the same finders are used for locallv originated and incoming calls, an incon ing call causes the marker to operate with fewer than the normal number of, or with no discriminating digits. The invention is described with reference to a 100-line rural office, an automatic satellite, a semi-automatic satellite in which calls are controlled by an operator at the main office and a P.A.B.X. The drawings should be arranged to make up circuits for these offices as shown in Fig. 19. All the systems use power-supply equipment, and allotting switches and line circuits of identical type and all employ finder-connector links of a generally similar kind. During the tens selection the connector chases the marker, being prevented from getting ahead of the marker and finally stopped by means of " jamming circuits " over which the driving magnet of the conversation switch is held energized. Means are provided for releasing permanent calls and locking the faulty line away from the exchange circuits. Similar but somewhat simpler circuits are described with reference to drawings in the Provisional Specification. Call-finder LFS. On the operation of a line relay L, Fig. 1, the starting relay ST, Fig. 6. locks itself in series with impulse relay A of the preselected link and in parallel with the normally energized relay DT in the allotter so that A pulls up and DT falls. Following this, B in the link energizes the common test and stepping relays TA, TB in series with the switching relays KA, KB which do not operate in this circuit. TA, TB jointly energize the driving magnet LFM which then releases them and interaction continues until a calling line is reached whereupon KA or KB pulls up in series with CO, L, of that line, short-circuits its high-resistance winding to energize CO and switches through. CO cuts off the line winding of L which however remains held in series with CO. Allotting new link. On the relapse of ST a circuit is made for magnet CDM from the contacts b3 of any idle links (KO holding in parallel). At the end of its stroke, CDM allows DT to pull up by removing a shortcircuit and is thus released. Interaction goes on until wiper la finds battery and 4a finds earth, whereupon DT holds up and KO falls. Rural office-discriminating function of marker. The 1st or 1st 2 or 3 digits are repeated to the marker magnet MRM and relay C in parallel. C energizes CR which energizes F. After the marker goes off normal there are self-interrupting driving circuits for the conversation switch via terminals 26T.. 30T, which are jumpered to 63T or 62T in accordance with the allotment of numbers to single and party lines. At the same time, jamming circuits are prepared or made via the conversation switch bank 8e which is crossconnected with the banks 3d, 4d, 5d of the marker. If the digit determines that the call is an external one, the conversation switch is stopped on the terminals preceding those of the 1st junction of the wanted group and on the relapse of C there is a circuit for JS via terminal 70T and the marker bank Id. JS locks, holds CR and cuts MC into the jamming circuit. MC locks and breaks the jamming circuit allowing the conversation switch to move on to the Ist junction, releases CR and energizes TC. If on the other hand the call may be local there is no circuit for JS, CR falls, and there is then a circuit for MH via terminal 61T and the marker bank 1d. MH opens the jamming circuit and makes a selfinterrupting circuit for the marker via wiper 6d. The marker moves to its next starting position in which MH is unlocked. In a similar manner the 2nd digit may route the call externally (if wiper 1d stops on a terminal in the 2nd half of the bank jumpered to 70T) or, if the call is local, similarly causes the operation of MH and the advance of the marker to its normal position. In this position the local-call relay LC is operated in series with a holding winding of MH and connects up the marking wiper 5d. Completing external call. If the 1st junction is busy, HC is short-circuited and the driving circuit is maintained over wiper 5e and 11 or col, the junctions having the same line circuits as subscribers except that the PN, PJ connections are crossed at the distributing frame. When an idle junction is found, HC pulls up in series with CNM, cuts off TC, and energizes H in series with CO, L in the junction circuit. H locks over its low resistance winding, energizing CO, L. Ground, temporarily connected to the lower wire, prepares the distant. office which is held subsequently by the bridge I, DJ. Subsequent digits are repeated at a2. If all junctions are busy, the switch is stopped on the last, the PN-PJ1 jumper of which is omitted, and since H remains unoperated, F falls and sends back busy tone. Completing local calls. The third digit drives the marker as before and the conversation switch chases it being finally jammed in a circuit over 5d. On the release of C, CR, MC is cut into the jamming circuit and the conversation switch moves one step. MC locks up and transfers the impulse circuit to the conversation switch magnet for the final digit. In the interval between the relapse of C, CR after this, a circuit is made for TC which locks and energizes HC which completes the test circuit. If the line is idle, H pulls up in series with L, CO in the wanted line circuit, shunts its high resistance winding, energizing CO, L, and releases TC, F, LC. Continuous ringing current goes out on the relapse of F until the relapse of LC and after that intermittent ringing current until the called party replies when F pulls up and completes the talking circuit. If the line is busy, H is unable to pull up and the relapse of F connects up busy tone. Incoming calls. Incoming junctions appear in the ordinary call-finder banks but since they have a strap in place of the meter between the terminals M, M1, the operation of CO energizes JD which prepares the link circuit for the reception of one or two digits fewer than the normal number. In the latter case, terminals 65T, 66T are strapped and JD energizes LC at once. In the former the marker responds to the 1st digit received and is chased by the conversation switch under control of wiper 4d after which JS or LC is energized as in a locallyoriginated call. Zero calls. When O is dialled, a circuit is made for MO (there being a jumper between terminals 10T, 69T), which is followed by JS, MC, TC and the conversation switch hunts for a junction as in the case of other outgoing calls. In this case, however, the feed relay D is connected to the junction instead of the bridge DJ, I. D operates when the operator plugs in. Calls to P.B.X. P.B.X. lines except the last have a strap between their terminals PJ, PJ1 and the conversation switch when set to a P.B.X. group hunts as for a junction. Metering. Normally the meter is operated by the answering supervisory relay D and remains held in series with JD independently of D. Metering is prevented in zero calls by MO. In junction calls D is operated by DJ. Satellite office-discrimination. As soon as the finder switches through, IJS pulls up and starts the conversation switch in search of a junction. When an idle junction is found TX pulls up and locks in series with TY which short-circuits TX. A temporary circuit is thus made for 1H which locks in series with CO, L and energizes 1F which bridges the junction. If all junctions are busy TX on falling back connects up dialling tone. The system as shown is arranged for 5 digits, but can be adapted for 3 digits or 4 digits by running jumpers between T65 and T66 or T66 and T67 to provide circuits for the local call relay 1LC after one or two digits. The first 1, 2, or 3 digits drive the marker and are repeated over the junction. While a call may be local (as determined by the jumpering between banks 3g, 4g and the terminals T56, T61) circuits are made after each digit for 1MH which, as in the rural office circuit, controls the advance of the marker to the next starting position. When it is determined that a call is non-local the relapse of 1C energizes a junction calls meter on T56 and the relapse of 1CR energizes 1LZ which disconnects the marker magnet. In the case of local calls, 1LC is operated when 4g moves to its next starting position after the 3rd digit and releases 1JS which releases TY, 1H. Completing calls. The last two digits control the marker and conversation switch in the manner described in connection with the rural office. On the relapse of 1C after the final digit 1LZ is operated re-energizing TX which energizes TY. TY unlocks TX, 1F, and a momentary test circuit is made over which 1H operates if the line is idle. Other operations take place as in the rural office. Semi-automatic satellite ; local and outgoing calls. The start relay ST is energized in series with BS which energizes 2F and drives the junction finder JFS off-normal. Magnet JFM continues to interact with 1B until an idle junction is found. Separate incoming and outgoing junctions may be provided but in the case assumed, the same junctions appear in both capacities in the banks of JFS, the test terminals corresponding to the 1st appearance being connected to P1 of the line circuit and those corresponding to the 2nd appearance to PN1. Assuming none of the junctions is calling at this time the switch pas