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Fig. 5 x 5480 Line-finder rack with 100-line finders of 1915 Hultman system and lower sides of the beams. The vertical movement of the wiper was obtained by means of a rack fitted on the wiper and a toothed wheel engaging same, this being moveable along- a shaft extending along the horizontal beams but rotating with the shaft when this was revolved. At the back of the beams, as also on the selector wiper, a number of contacts was mounted to control the movement of the selector horizontally. The connecting bank of this selector was divided into four sections, each with 2 500 subscriber linos, distributed in 50 frames of 50 lines to a frame. Of these four sections one was placed above and to the left of the selector wipers in normal position, one above and to the right of the wipers and the two others below the lower end of the wipers, one to the left and one to the right. Trials with this system were carried out at L.M. Ericsson & Co's, with the collaboration of Martin Lojgrcn and Sigurd Johanson. A first trial plant was demonstrated on 26th January, 1915, for the head of the Telegraph Administration, Director-General Herman Rydin, and members of the Board of Telegraphs. In 1910 Aktiebolaget Autotelefon Betulander was established, constructing automatic exchanges on a relay system designed by Betulander. It was later reconstructed as Nya Aktiebolaget Autotelefon Betulander and was finally taken over by Telefonaktiebolaget L.M. Ericsson. While Hultman and Olson were each working separately for the production of an automatic system, the same problem was also occupying Betulander and his collaborators, among whom may be especially mentioned Nils Palmgrcn, who along with Betulander appeared on a number of patent applications of those days. The designing activity thus proceeding along three different lines led rapidly to appreciable results and by 1915 the Telegraph Administration considered it desirable to carry out comparative tests in practical operation. A little while before — in 1913 — the Administration had purchased from a foreign manufacture a semi-automatic exchange which was put into service in 1915 at Landskrona. The first Hultman exchange, a semi-automatic exchange for 1 000 subscribers, was ordered from Aktiebolaget L.M. Ericsson & Co under contract dated i6/25th June, 1915, to be delivered and installed in Stockholm within twelve months. There was concluded on 20th August, 1915, an agreement with Nya
Aktiebolaget Autotelefon Betulander for delivery within ten months of a semi-automatic telephone exchange on the Betulander relay system for I ooo subscribers. An Olson exchange for 200 numbers was ordered later the same year from the Telegraph Administration workshops. The Hultman exchange comprised in addition to the 10 000 line selector a rack with line finders and an impulse machine, a rack with sequence switches and registers, a keyboard position for the semi-automatic switching and a B-position for the incoming traffic. The line finders, Fig. 5, were mounted together in groups of ten, with a common bank consisting of bare wires laid horizontally, arranged in one plane on the front and one on the back of the frame common to ten finders. The line-finder bank comprised 100 subscriber's lines with four wires for each subscriber. The movable connecting organ consisted of an endless, flexible steel strip which by means of mechanical force was made to run over two discs one above and one below the contact bank. On the strip were fixed four studs of insulating material which as the strip moved acted succesively on springs located in front of the wires of the bank so that contact was made between the respective wires and the contact springs. The series switches consisted of a number of discs of insulating material fixed on a shaft, which as the shaft turned under machine drive produced the contact combinations necessary for switching. There were three sequence switches for each final selector. The step-by-step driven registers were operated by means of the impulse machine controlled by the keyboard and restored to home position by impulses from the final selectors. The exchange was in service with about 300 subscribers from the spring' of 1918 up to and including July 1920. It operated satisfactorily in the main, particularly when it is recalled that it was put into service practically without preliminary experiments. Hultman, however, even before the exchange was opened had realized that alterations should be made, as is clearly evident from a report of an inspection of the exchange in January. According to this report Hultman received the inspection committee with the following declaration: »finders of the design fitted should not be further employed; new sequence switches should be fitted, new registers, new keyboard positions and new final selectors are to be designed; the capacity of the multiple should be reduced to 2 000 lines, the impulse machinery could be dispensed with, a system of reports for fault signals should be introduced etc.» The inspection committee was convinced and recommended in its report that the system indicated by Hultman appeared in several respects to be »so simple and ingenious that the experiment should be proceeded with*. In the Olson trial exchange, which as stated was arranged for 200 subscribers, there was employed an unusual form of selector design, a kind of combined pre-selector and line-finder. Each subscriber line was connected to such a combined selector, which for outgoing call was used to hunt for a disengaged link circuit and for incoming call to hunt a reserved line in the group selector multiple. This last function was unique. These pre-selectors were 30-line selectors with two sections of contact points, one for outgoing and one for incoming traffic. The distribution might be done arbitrarily so that, for example, twelve numbers could be used for incoming and eighteen for outgoing traffic. For register selectors, group selectors and other devices required for building up the connection throughout the system there were employed both 10-line and 30-line selectors. The selectors were rotary and had not more than 33 contacts in the multiple bank. On call from a subscriber his pre-selector was started, hunting a disengaged link circuit and afterwards obtaining connection over a register selector with a selector. Since the system was arranged for semi-automatic operation at the trial exchange, connection was made over the register to a keyboard operator who took the subscriber's order and set the register in accordance with it (the system could easily be converted to entirely automatic, in which case the register was operated direct by the dial impulses of the subscriber). The numerical group selectors were arranged on an intermediate selector system, i. c, the selectors over which calls were exchanged were 97
Page 3 and 4: ERICSSON REVIEW Responsible Publish
Page 5 and 6: the pioneers of the guild of teleph
Page 7 and 8: Fig. 1 XS869 The BetulanderandPehrs
Page 9: in which case the connecting" devic
Page 13 and 14: that the system was not adopted for
Page 15 and 16: All the apparatus necessary for the
Page 17 and 18: Fig. 1 Repeater racks X547T right t
Page 19 and 20: Fiq. 3 & 4 x « Rocks in detail lef
Page 21 and 22: Fig. 6 * 7«i5 General diagram for
Page 23 and 24: x n Fig. 9 Connecting diagram for
Page 25 and 26: \ Fig. 12 xi Intermediate repeater
Page 27 and 28: grasping of the speech from the dis
Page 29 and 30: Portable Telephone Instruments E. B
Page 31 and 32: highest efficiency is obtained with
Page 33 and 34: This is done by pressing in the key
Page 35 and 36: \ Hotel Switchboard K. G. H A N S 5
Page 37 and 38: \ New Ericsson Wireless Receivers B
Page 39 and 40: \ The sensitivity of the apparatus
Page 41 and 42: Ericsson 380, Fig. 6, is a single c
Page 43 and 44: \ For a time gelatine appeared to m
Page 45 and 46: S Recording The attainment of good
Page 48: The Ericsson Group Associated Enter

contents - History of Ericsson - History of Ericsson

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