577,648. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., McCLEW, J. W., and PEARCE, O. A. April 1, 1944, No. 6083. [Class 40 (iv)] Interworking between an exchange operating on a direct setting decimal basis and an exchange operating on a revertive control non- decimal basis is catered for by the provision at the latter exchange of temporarily-used converting apparatus. In Fig. 1, RE is a 10,000 line revertive exchange of Ericsson type employing 500-point " around-and-in " switches while SE is a 10,000 line direct setting exchange of Strowger type, and it is assumed that the exchanges form part of a 5-digit linked numbering scheme in which numbers beginning with 9 are allocated to the exchange RE and those beginning with 8 to the exchange SE. As shown in Fig. 2, each selector at the exchange RE has 25 levels of 20 outlets each, and the various levels of the first selectors 1RGS give access to different exchanges. Twenty levels are utilised on the second selectors 2RGS1 to give access to the final selectors RFS serving the wanted 500-line group. If, for example, the dialled number is 90499, it will be seen that the selectors send back to the register R four non-decimal impulse trains comprising 8, 1, 25 and 20 impulses. Calls from RE to SE are set up with the assistance of a converter C which becomes associated with the outgoing relay set RORS and sends non-decimal revertive impulses to the register R and then decimal forward impulses to control the selectors 2SGS2, 3SGS, SFS at SE. Calls from SE to RE are set up with the assistance of a translator T which becomes associated with the incoming relay set R1RS and receives decimal impulses from the outgoing repeater SORS and non- decimal revertive impulses from the selectors 2RGS2, RFS at RE. The outgoing repeater SORS serves to guard the junction until the called party clears and the equipment at RE restores, this being necessary as the revertive exchange operates on a last party release basis and the step-by-step exchange on a calling party release basis. Call from RE to SE. Outgoing relay set RORS, Fig. 1. Relay JT energizes over the c wire upon seizure and an idle converter C is taken into use by the switch CH, the incoming a and b wires and the junction wires being extended thereto by switching relay KA. When the converter has completed its operations, relay SZ energizes and switches the incoming a and b wires through to the junction. In response to battery reversal upon reply, relay D grounds the c wire and holds JT, so that the junction is not freed until both parties have cleared. Converter, Figs. 4-9. Start relay T energizes over wire SW and connects up TA. When the register R is ready, relay SR energizes over the b wire and connects up PR which acts as a stepping relay for the switch VG and controls relays RP, RQ to send an impulse over the a wire for each two steps of VG. The revertive impulse switch in the register R moves two steps per impulse slightly in advance of VG until a marking is reached, when SR is dis. connected and VG takes a final step to line up. The switches VV, RV are set in a similar way in positions 2, 3 of the sequence switch DD. Since VG determines the required 500-line group and VV the required 20-line group, the thousands digit is marked over wiper VG2, the hundred's digit over wipers VG3, VV2, VV3, the tens digit over wipers RV3, VV4, VV5 and the units digit over wiper RV2, the connections being made as shown to the marking wires 1 ... 9. In addition, for the digit O the sending switch SS is given a permanent marking which is effective when there is no marking on the wires 1 ... 9. Assuming that terminals 12, 13 are strapped (see below), the sending switch SS goes to its next home position as soon as the converter is taken into use. With the sequence switch DD in position 2, that is, as soon as the switch VG is set, relay MC energizes and connects up RC, which steps the switch SS and delivers impulses to the receiving magnet RM of a mechanical impulse regenerator of the kind described in Specification 458,095. Relay ST pulls up when the marking corresponding to the thousands digit is encountered, whereupon MC, RC fall back, the marking magnet. MM is released and SS goes to its next home position. In a similar way the hundreds digit is transferred in position 3 of DD and the tens and units digits in position 4. At the first release of the marking magnet MM, relay BY energizes and connects up the sending magnet TM, whereupon the stored digits are emitted in the customary manner at impulse springs M, the inter-digital pause being taken care of by relays IP, IS. When all the digits have been sent, relay ES operates on the release of BY and connects up SZ in the relay set RORS. If the junctions go to first selectors at the stepby-step exchange or to second selectors at a 6-digit exchange, a fixed prefix digit must be sent. This is provided for in the converter by strapping terminals 10, 11 instead of terminals 12, 13 and connecting terminal TTM to the appropriate marking wire. Relay MC then operates when the converter is taken into use and brings about the storage of the prefix digit in the regenerator. Call from SE to RE. Outgoing repeater SORS. Upon seizure, relays A, B, J, JA (Figs. 11, 12), and BMD energize in turn, the junction is looped and impulses are repeated thereover in the usual way. Relay BB operates and locks when impulsing begins. Relay BD responds upon reply and disconnects BMD, whereupon reversing relay DD pulls up and applies booster battery to the P wire during the relapse of J, JA. Should the calling party hang up first, relay BD remains held over the junction and therefore J re-operates and brings up BMD to guard the junction until it is released at the called end. In the case of premature release or under artificial busy conditions at the revertive exchange battery on the positive wire brings up relay G and hence BMD. Incoming relay set, RIRS, Figs. 13, 14. Line relay CA connects up CB which grounds the c wire to seize the incoming selector 2RGS2 and causes an idle translator T to be associated over the switch TH, switching relay CKA being operated. While this is taking place, incoming impulses are received by the receiving magnet CRM of a mechanical impulse regenerator. When the first digit is complete, the relapse of dialling relay CC connects up CBY, provided the translator is associated, whereupon the sending magnet CTM starts to transfer the record over wire IMP to the translator at impulse contacts M. Relays CIP, CIS take care of the interdigital pause and send impulses over wire DD to control the in-sequence switch of the translator. When the selectors have been set under the control of the translator, relay CSZ operates, releases the translator and puts line relay CA under the control of CD, which is shunted down upon reply and reverses the connections to the incoming junction. Relays CG, CSZ are held until the called party hangs up to maintain the guard on the junction at the step-by-step exchange. In the case of premature release, the regenerator receives an impulse, and the release of CB frees the translator and connects up CSZ to guard the junction until the regenerator is normal. The junction may be artificially busied by the operation of CSZ over a test jack or by the connection of battery to the positive wire when the relay set is removed from the rack. Translator T, Figs. 15-18. Start relay SA energizes over wire SW, connecting up SB, TR, and the out-sequence switch RD goes to position 2. The impulse trains from the regenerator set the switches M, C, D, U in successive positions of the in-sequence switch DD, and when the thousands and hundreds digits have been recorded, TR is disconnected and RD goes to position 3 in which battery is applied to the b wire to start the selector 2RGS2. The switch PG goes to position 2 and then advances two steps per impulse in response to revertive impulses over the a wire which control relay RP until it picks up a marking over wipers C3, M3, M4 corresponding to the required 500-line group. Relay PCO responds and stops PG, and the final operation of RP connects up PCE which opens the b wire to stop the selector. In a similar way, the switch VV is stepped by revertive impulses until it encounters a marking over wipers C4, D3 determining the 20-line group and the switch RV is stepped until it encounters a marking over wipers D4, U3, both these sets of impulses coming from the final selector RFS. These operations take place with RD in positions 6, 9 respectively. Finally, RD goes to position 13 in which wire SZ is grounded to operate relay CSZ in the relay set RIRS.