Patent GB-584590-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/42
Filed: 1945-01-06
Abstract: 584,590. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and CHRISTIAN, D. A. Jan. 6, 1945, No. 576. [Class 40 (iv)] Selecting switches are set by markings applied in a control circuit between the line circuit and first selector which may be associated either temporarily or permanently with the first selector, the marking wires being switched through by each selector in turn to the banks of the succeeding selector and all the markings being set up in turn by one marking switch. The invention is applied to an arrangement in which marking is effected by the choice of two out of three marking wires, discrimination according to polarity being included,' the same coding being used for the respective digits 6-0 as for 1-5 and separate discrimination between these two sets being arranged for by driving the selector to the " mid-normal " position for the former set. Alternatively, markings may be had over four or five wires in combination with discrimination by polarity or by the " midnormal " principle. Marking. The selectors are single-motion, power-driven, 52-point switches having in some cases staggered wipers as shown by full and dotted lines, which in a full revolution sweep over 104 contacts. Where the wipers are shown as two full lines, the wipers are not staggered and sweep over the same set of contacts twice. Code connections are made to the marking wires XYZ on the group selector banks 4 and 5 (Fig. 2), and on the tens banks 8 and 9 and, units banks 6 and 7 of the final selector (Fig. 3). The 51st or " mid-normal " position of the first (full line) are to be swept in any selector is marked on the X and Z wires so as to operate relay PT to stop the selector on this position. Markings applied after the aperation of the selector switching relay to the X and Z wires are used in the case of junction outlets from a group selector to effect operation of a junction switching relay. For busy signalling purposes the normal contact and 51st contact of the later (dotted) are to be swept are connected in the bank 4 to the marking wire Y. Group selector. In the control circuit, Fig. 1, the usual relays A, B and C operate on seizure and the magnet MD of the digit switch MS steps in response to the incoming first digit and dialling relay C on releasing connects test relay T suitably poled by rectifier MR1 to two of the marking wires XYZ. Holding relay GH operates and locks to earth on the p-wire. If the digit is less than 6, the selector magnet GL operates to earth applied to the a-wire on release of C and the motor-driven switch hunts for an idle marked outlet, negative battery on whose p-wire, when found, operating the highspeed test relay T which is connected across the appropriate pair of marking wires by wipers MS1, MS2. T operates the high-speed auxiliary test relay TT and also R, and shunts out its lower (high resistance) coil, earth over its upper (low resistance) coil and the marking wires being applied to the p-wire to busy the outlet. If the digit is over 5, earth is applied to the a-wire over MS3 as soon as the 6th impulse is received and the selector moves to its 51st position to operate PT to step the selector until C releases, whereupon the selector switch hunts for an idle outlet in one of groups 6-0. Positive battery thus applied by TT to the p-wire operates the selector switching relay GS which releases T, thereby completing a circuit for the release magnet MR of the digit switch MS. Relay GS switches the marking wires through to the next selector. Relay TT releases to earth the p-wire before the switching relay in the next selector has time to operate. If all outlets of a required group are busy, the selector rotates either to the normal or the 51st position of the dotted arc. In the former case, high resistance positive battery applied from the p-contact and thence along the Y wire operates BS in the control circuit which brings up BT to stop the selector on this position and to send back busy tone. In the latter case, low resistance positive battery from the pcontact operates BT direct. If the particular outlet is a junction, relay J operates to battery and earth applied over wipers 8, 6 when GS switches through and connects in the looped back bridge relay D and subsequent impulses are repeated by A out to the junction. Final selector. The incoming tens digit sets the marking switch MS in the usual manner and T and TT operate to stop the selector on the first contact of the required decade, a preliminary movement to the " mid-normal " position taking place if the digit is greater than five, as in the group selector. Positive battery on the p-wire operates FT (which locks locally) in the final selector during whose change-over relays T and TT release before FU can operate. Relay FT operates E over the b-wire. Release of T releases the marking switch which is then re-stepped by the units digit during which C operates F and releases R. A preliminary movement to the 6th contact of the decade takes place as for the movement to the " mid-normal " position above, if the units i digit is greater than five. The final selector searches for the marked line at which T, TT and R operate, and also FU in the final selector to connect negative instead of positive battery over the b-wire to release E. FU holds in series with PB which does not operate. Relays T and TT are released during the transit of FU which then immediately connects T to the test wire of the called line. If free, T and TT are re-operated and T busies the called line. When E releases, S operates and locks and connects positive battery to the p-wire to operate switching relay FS in the final selector, thus releasing T and TT. Relay S switches the a- and b-wires through to the ringing source applied over relay TR which operates and locks to answering subscriber's loop which is then connected to the feeding bridge. Back bridge relay YY operates and connects positive metering battery to the pp-wire during the slow release of L. If the called line is busy, BT operates on release of E to revert busy tone and release the marking switch. Since, when the units digit 6 is dialled, the switch rotates to position 6 (under control of PT), the switch must be .prevented from moving off on release of C. A contact of F therefore changes the code to ZX on release of C to effect immediate operation of T. In the case of the 1st and 6th decades, a separate stopping contact on the switch for the tens digit is provided, lest T should not release during the change-over from the tens to units marking bank, which might result in wrong seizure of lines 11 and 61. In all other cases the first line of the decade may be safely used as a stopping place. PBX hunting. Corresponding contacts of banks 4 and 5 of the final selector are connected for all outlets of a PBX group except the last. If the first outlet is busy when FU operates, the additional current (from wipers 4 and 5) in the b-wire operates PB in the control circuit. PB operates PC which advances the marking switch a step and also causes PB and FU to release due to the inclusion of the second coil of PB in its circuit. Release of FU re-operates E and reconnects the marking wiper 6. Relay E releases R to earth wire a and operates selector magnet FL. Relay R releases PC. The final selector steps to the next outlet of the group which is now marked by MS and proceedings repeat themselves until on stepping to a free line T and TT operate, to operate S instead of PC. If all outlets are busy, PB does not operate on the last outlet and BT operates instead of PC to revert the busy signal.