761,068. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. July 19, 1954 [Aug. 7, 1953], No. 21810/53. Class 40 (4). One of a plurality of registers transfers dialled digits to control equipment common to the registers, the control equipment then selecting from a plurality of groups of outlets a group of outlets leading to the desired destination and causing available ones of the outlets of the desired group to be marked in a high speed electronic hunting circuit, which hunting circuit takes into use the first available outlet. The invention is applied to a nation-wide system. By dialling a first digit " 1 " access is had to the extended area over the first level of the first group selector 1GS, Fig. 1, to seize a level relay set LRS and make connection to an electronic register REG. This connection is first made over an electronic path RC for the initial transfer of information, an electromagnetic path being subsequently established for transmitting outgoing impulses from the register. When the exchange digits C, D, E have been stored in the register a high-speed electronic finder TRF makes connection to a translator TR which sets up the appropriate routing digits in the register. At the same time the translator selects an idle junction relay set JRS in the required group by a high speed hunting operation and selects a free path to it from the level relay set LRS through primary and secondary switches 1TS, 2TS. The translator also sends metering information direct to LRS or JRS and determines whether setting up the call should be completed by the initiating exchange or by a register in the distant exchange. In the latter case the necessary information is transmitted as coded v.f. pulses by a high speed sender S. Translator, Figs. 4, 5. The exchange digits C, D, E are converted by the register into code markings on leads W, X, Y, Z and are reconverted to decimal form by converters CC, DC, EC in the translator. They are then translated into routing digits as described below and sent back to the register in code by converters 1RDC-4RDC. Leads ORD, CCB identify the class of the calling party. Leads NW, NX, NY signal back the number of numerical digits required to follow the routing digits. Leads SW, SX signal whether high speed or dialling speed sending is necessary, and lead AOB is marked if all outlets are busy. Electronic translation. The translation arrangement uses 10 blocks of 100 cold cathode triodes 1TF-10TF. The first code digit C applies anode potential to all the tubes of the related hundreds group. The third code digit E applies priming potential to the trigger electrodes of the related horizontal groups of ten tubes in each of the hundreds groups. The second code digit D applies an operating pulse to the related vertical groups of ten tubes in each of the hundreds groups. Accordingly, only one tube strikes to mark one of a group of terminals CDE1-CDE1000. Each terminal is strapped through a related FP terminal to a group of isolators comprising cold cathode tubes LR, RD1, RD2, NN, SN, MF. Class of service. According to the type of subscriber, signals from the register on lead ORD and/or CCB energize relay AA and/or BA. If the destination represented by the selected terminal FP is barred to the calling subscriber, terminal B is strapped to terminal HT so that only isolator FP fires to strike a tube in manual board reverter MBR, so directing the call to an operator. Assuming, however, that the call is permitted to all subscribers, HT is supplied to all the isolator tubes. Tube LR strikes to pulse lead PU after a delay to cause idle route selector secondary switches to extend markings over leads MK to high speed hunt HSH2. HSH2 responds to a pulse from delay network D1 to seize the first idle route from the level relay set LRS to the selected junction relay set JRS, Fig. 1. Routing digits are handled by one or more isolators RD1, RD2 which are strapped to corresponding discriminators 1DISC, 2DISC. Each discriminator comprises 100 pairs of gas triodes to mark leads leading to routing digit converters 1RDC-4RDC. In the case of an odd routing digit RD1 or RD2 is strapped directly to the appropriate terminal 1D1-1D10 or 3D1-3D10. An isolator NN signals to NDISC the number of numerical digits to follow the routing digits. NDISC signals this number in code over leads NW, NX, NY. Isolator SN indicates through SDISC to leads SW or SX whether impulsing should be at dialling or high speed. Metering. Whatever the class of the calling party, MF operates metering discriminator MDISC according to one of 15 rates, the rate being converted to binary form at MFC and applied over leads WF-ZF to set up a group of cold cathode tubes associated with the junction relay set JRS. Release. If all outlets are busy, the high speed hunt HSH2 energizes lead AOB to release the translator. Also, a predetermined time after the translator is taken into use a tube CHV (Fig. 6, not shown) strikes to release the translator irrespective of whether it has operated or not. If it has not operated, lead AOB is energized to return busy tone to the calling subscriber. Specification 761,120 is referred to.