These notes were originally produced in 1987 to mark the 75th anniversary of the opening of Britain's first public automatic exchange. This event occurred in 1912 and following received wisdom, I assumed that this was the year in which automatic telephony took root in this country. Indeed, Britain is often accused of being slow to adopt new technology for its telephone service, and the delay of twenty years between the introduction of the first automatic telephones in the world (La Porte, Indiana, USA) and Epsom's inauguration is sometimes cited as evidence.
A little research, which grew into a lot of research, led me to uncover new facts which now alter and correct that impression. It also meant that it was impossible to bring out this booklet during 1987. All the same, for the first time in print it can be reported that Britain's automatic telephone history goes back somewhat further than assumed, in fact to 1898, when the first dial telephone installation was ordered. The rest, as people say, is history - and as far as the first twenty years are concerned, most of it is in this paper.
The paper does not go into great technical detail, though it does point to the appropriate references. Nor does it attempt to provide a history of the telephone service in general, and the broader background as well as the commercial and social development of the telephone in Britain is left to be found in the reference books cited. What it provides is a concise record of the history and development of automatic switching technology during a period which has received little attention hitherto.
It is entirely intentional that this is not a balanced study, and some developments have been devoted more space than their overall significance deserves. This is deliberate because up to now these systems have gone unrecorded in telephone literature, and it would be a shame if technically ingenious but commercially unsuccessful systems were denied a place in history. In other words, this is more of an connoisseur's or enthusiast's guide than a strictly academic historical text!
Where primary information is scarce I have perforce had to leave some gaps, hoping that others will follow up the clues and, hopefully, have more success in tracking down the information. I shall, of course, be delighted to receive any feedback at firstname.lastname@example.org . Many abbreviations are used in the text, and all are explained at the end. Acknowledgement is readily made to all previous authors on this subject and to the Journal of the Institution of British Telecommunication Engineers, from which some material has been adapted.
It is impossible to treat a subject as complex as this in purely chronological order. I am, in any case, reminded that a mere chronology is of little value since it cannot indicate either the significance or the influence of events. In some cases I leave evaluation of the latter to cleverer minds. It is clear, though, that in the British Isles we have had one of the most varied and interesting systems in the world and it has been a pleasure to record some of its technical development.
It is commonly agreed that the first fully automatic switchboard used in Britain was one patented by Mr D. Sinclair, when engineer for the National Telephone Company in Glasgow. Although it predated the well-known work of Strowger in America, it was not such a significant development. This is because Sinclair's invention was not a complete telephone exchange, more of a remote-control switch . Today we would call this concept a line-connector or a remote concentrator unit. The apparatus was for single wire circuits only, and was efficient for one junction line and five subscribers' lines. When a subscriber called his indicator made contact with a sliding bar which connected the calling line to the junction line leading to the central exchange, and insulated all the other lines.
According to a paper read by Aitken in 1911 and his Manual of the Telephone, the first of Sinclair's switches was installed in Glasgow in 1883 and a few of these were in use in Scotland for a while. Parts are believed to survive in the National Scottish Museum, Edinburgh.
Before this time, the concept of a complete automatic telephone exchange had already been contemplated in the USA, the home of the telephone. Already in 1879 a patent was issued to Connelly and McTighe for a system embodying step-by-step mechanisms controlled by impulses from the telephone, but it was crude and impractical. In the same year Westinghouse described an auxiliary exchange which, like Sinclair's, enabled suburban telephone users to obtain the sole use of a junction circuit to a city exchange.
In 1883 a Mr A.S. Paul acquired the English rights of a step-by-step system invented by the Swedish Ericsson company, but this too was only a remote-controlled selector or auxiliary exchange enabling a city operator to call a particular rural subscriber.
The breakthrough came in 1891 when Almon B. Strowger of Kansas City obtained his first patent for an automatic means of communication between two subscribers
(see pictures). This contained the basic idea of a selector finger moving both vertically and horizontally to reach any one of 100 lines arranged in ten rows each containing ten lines. The selecting finger was moved by electromagnets which, in turn, were controlled by current impulses sent by keys on the calling subscriber's telephone. At this stage separate wires were required for speech and for the hundreds, tens and units keys, making five wires in all.
The story of an undertaker's lost business surrounding the invention of this solution to the problem of unreliable manual operating is too well known to bear repetition here, nor is there room to describe the gradual refinement of the Strowger system into a commercial dial telephone system using first three, and then two, line wires. These are described in other telephone literature [for instance Robertson's The Story of the Telephone], together with the opening of the first public automatic exchange in La Porte, Indiana in 1892. An important innovation was made in 1896 when the keys used for signalling numbers to the exchange was replaced by the dial, in essence no different from the one used today. In the following ten years more than seventy automatic exchanges were installed in the USA. In Britain interest was stirring, too.
The advent of fully automatic telephone systems did not, however, extinguish interest in so-called semi-automatic operation. For a decade or more argument raged as to whether subscribers were capable of "spelling out" their numbers to automatic equipment and whether control of sophisticated apparatus was not better left to trained operators. Indeed, some foreign installations made subsequently relied on subscribers passing their wanted numbers to operators, who then dialled and rang the numbers. There were many experts, too, who considered that the process of dialling a number, the risk of human error ("finger trouble") and waiting for the automatic equipment to complete its machinations was tedious and could be beaten easily by human operators.
In this connection it is therefore worthy to give brief mention of a semi-automatic system put forward by a Mr A.M.T. Thompson and exhibited at GEC's premises during 1901. In this system the number required was set up on the subscriber's instrument and sent as impulses to the exchange so as to display the number on an electromagnetic counter. The operator would then connect to this number in the usual way. In fact the system was never adopted commercially.
THE FIRST STROWGER INSTALLATIONS
The automatic telephone system, Baldwin tells us, was first introduced to the United Kingdom in 1897, when representatives of the Strowger Automatic Exchange Company of Chicago brought over to London a working exhibit of 200 lines capacity. This was set up at Winchester House, 66 Old Broad Street in the City of London, where the system was exhibited for the first time on this side of the Atlantic. This particular installation provided for each subscriber's line to terminate on a two-motion switch and a multiple of all the subscribers' lines appeared in front of each switch mechanism. The exhibit attracted considerable interest, but on account of its capacity being limited by the size of the multiple, it was considered impractical for large installations.
A company called the Direct Telephone Exchange Corporation Ltd., based at 84 Winchester House, was formed to exploit and popularise the Strowger system. It published an informative booklet and arranged for a demonstration of the system at the Royal Institution in June 1898. Exchanges for 100 and 400 lines, also for 1,000 and 10,000 subscribers were described. The same syndicate also made presentations to Prussian and Bavarian delegations, who came to London in 1898 for this purpose. Representatives of the Automatic Telephone Exchange Company of Chicago were also present on these occasions.
It was at this time that the first sale was made of what the Americans at that time widely called "the girl-less, cuss-less telephone". This episode does not appear to be mentioned in the contemporary literature. Research in the archives of Glasgow City Chambers, however, indicates that the town council approved at a meeting held on December 13, 1898 draft heads of agreement between the corporation and the Telephone Construction Co. of 85 Winchester House, London. The company was to install an 'automatic telephone exchange system for twenty-five instruments', and maintain it for three months, all at their expense. If the corporation wished to have instruments placed in municipal offices outwith the City Chambers, however, this would be at their expense. At the end of the three months the corporation would have an option to purchase.
On January 13, 1899 the town clerk reported to the Special Committee on the Telephone Service that the company was prepared to proceed with the installation. Later, on October 13 a letter from the company was submitted, stating that the three months had expired and enquiring whether the corporation proposed to purchase. The committee agreed to wait until offices outside the City Chambers had been connected before coming to a decision. On March 27, 1900 they recommended that the installation be purchased, and this went ahead. The principal archivist of the Strathclyde Regional Archives notes that in July 1900 there are references to negotiations with the Strowger Automatic Telephone Exchange Co., Chicago, apparently in connection with a different system. This may, however, been for acquiring further components.
It is interesting to note that a municipal body was the first to adopt this new-fangled system of automatic telephony - perhaps it was a case of civic pride. Remarkably it contrasts with the rather outmoded call-wire system adopted for the Corporation's (manual) municipal telephone service; it would be interesting to research the background reasoning behind the two radically different decisions.
In 1899 another Strowger exhibit was received from Chicago, which embodied the principle of trunking and grouping used in all subsequent installations. This paved the way to systems of virtually unlimited capacity and was introduced simultaneously into France and Germany. A further private installation was made during this period, at some time before 1906 when it was mentioned in that year's edition of Poole's Practical Telephone Handbook. This was at St Bartholomew's Hospital, London, but extensive searching of their records has revealed no details of the exchange.
Another publication of 1906, The Electrician, recorded (on July 13) "It is stated in the Western Electrician that Mr Andrew Carnegie has purchased from the Automatic Electric Co. of Chicago a complete private automatic exchange equipment of 20 lines for his estate at Skibo Castle in Scotland. The first 13 lines are to be working by August." The system replaced an old manual magneto one and is described in greater detail in the July 1906 issue of Telephony.
The next event to note is the Exposition at the White City, London, in 1908 where a demonstration exchange embodying all the latest improvements was put on display. By this time the telephone line circuit had been refined to just two wires (like a normal CB manual telephone) and the large dial with oval slot-shaped finger holes was replaced by the small round dial with which we are still familiar. Automatic ringing, though with no tone to the calling subscriber, was provided together with busy tone for connection to engaged numbers. It was at this exhibition, too, that the British Insulated & Helsby Cables company first saw the potential of automatic telephones and became interested in manufacturing them.).
Indeed, the growing appreciation that machine switching, as it was also called, was the thing of the future led the British Insulated and Helsby Cables Ltd. to set up a separate company to manufacture equipment of the Strowger pattern. What had happened, incidentally, to the companies based in Winchester House in the meanwhile is not clear, but their lack of large-scale sales may have a bearing on their demise. As Robertson points out in The Story of the Telephone, Dane (christened Daniel) Sinclair was the key figure. Clearly, he had retained his interest in automatic switching after his early work in 1883.
Sinclair had been Engineer-in-Chief of the National Telephone Company (shortly to be taken over by the Post Office in 1912) and left that firm to go as General Manager to the BI&H Cable Company (now BICC). He had always been interested in, and - as mentioned in the previous chapter - was one of the first patentees of, the idea of automatic telephone systems. He urged his employers to acquire the British and colonial patent rights of the Strowger system. This was done in November 1911 - a few weeks before the NTC's operating licence expired - by the new Automatic Telephone Manufacturing Company, which was independent of (but had a reciprocal arrangement with) the cable company. [The Post Office, ever conservative, must have pretended not to note the distinction between the companies, since it used the manufacturer code H - for Helsby - for ATM products.]
The first action, made in November while the patents were still in the hands of the cable company, was to arrange a press demonstration of the automatic equipment. Illustrated features appeared in The Sphere and the Illustrated London News, together with sentiments such as "Every man his own exchange' and a system "which will entirely dispense with telephone girls". The Sphere's photographs indicate the table and wall phones used at the time, which used the old 'sunburst' eleven-hole dial. In this pattern, which was slightly smaller than those which followed, the finger wheel was disconnected from the dial mechanism once the user's finger had reached the finger stop and returned to normal at a high speed. The eleventh hole was purely decorative and served only the purpose of symmetry. The centre of the dial had a pressed sunburst pattern and no provision for a number and instruction label, a feature which was, however, introduced on the instruments used at Epsom.
Dane Sinclair was managing director of the new company, which took over the Edge Lane, Liverpool works and relevant staff of the B I & H Cable company. The new firm began its effective life on January 1, 1912 and set about designing and making press tools and jigs for the mass-production of automatic telephone equipment. The Automatic Telephone Manufacturing Company (ATM, later known as Automatic Telephone and Electric or AT&E, now part of Plessey) was thus the first firm to undertake the manufacture of automatic telephone equipment in this country. (Initially the operation was confined to assembly of components produced in Chicago. The first public exchange apparatus produced at Edge Lane was for Newport, opened in 1915.)
Despite, or perhaps notwithstanding, the experience of the early small private installations, 1912 thus stands out as the watershed year in the development of automatic telephony in Britain. This was the year when the ATM company opened for business and when the expanded Post Office (incorporating the NTC) ordered and opened two automatic exchanges. The time was now right for commercial exploitation of dial telephones on a proper scale.
EPSOM AND AFTERWARDS
By 1912 the Post Office had determined it was time to give automatic telephone switching a full investigation and a fair trial under practical conditions. In fact the decision was made to order three exchanges, two for public use and the other for internal application. Since ATM was the only company actively offering auto equipment in Britain it was natural that the Post Office should turn to ATM for the supply of apparatus, but the Strowger technique was not the only system of machine switching in vogue at the time. Three other automatic exchange systems, the Rotary (American), the Betulander (Swedish) and the Lorimer (Canadian) were being exploited elsewhere and the Post Office decided to make a trial of two of these.
The two ATM exchanges were to be installed at Epsom in Surrey, just south of London, and at Post Office headquarters in London, while the Lorimer would serve the Caterham Valley. The observation of the performance of these two techniques would supply the answers to some fundamental questions and enable a long-term policy to be established. The questions, to paraphrase Robertson, were:
(1) Would automatic apparatus function properly under British conditions?
(2) Would it offer the public any real benefit in service?
(3) Would the public take to dialling their own calls?
(4) Were the additional costs (if any) offset by the advantages (if any) of auto working?
(5) Which was the better of the two rival systems?
According to equally authoritative sources, Epsom auto exchange opened on March 13, May 18 or May 26, 1912, (the dates probably relate to contractor's handover, actual and official opening). This was followed on July 13 by the opening of the "Official Switch" at PO HQ, St Martin's le Grand. The opening of the Caterham Valley exchange was delayed, owing to the difficulty the contractors found in delivering the necessary plant. Its story is told in the next chapter.
Both Strowger exchanges followed standard USA practice in most respects, including telephone instruments embodying a direct current-energised magnet in the receiver (to save weight) and no induction coil. These arrangements were not retained in later systems, nor was the polechanger arrangement for producing the ringing current and buzzer and pendulum device for busy tone. It was realised that other arrangements could be modified to advantage, and engineers of the PO and ATM company started the long train of development which gradually led British automatic practice away from that of the USA.
The two 1912 exchanges used the current Strowger two-wire system and, not unexpectedly, gave very adequate service all told. Epsom provided for 500 subscribers initially, with an ultimate capacity of 1500. The Official Switch also had a long-term capacity of 1500 and was first equipped for 900 users. Using plunger-type Keith line switches and 'vertical' pattern group and final selectors, both exchanges were fitted out along similar lines, and in fact when Epsom was eventually closed, some equipment recovered from there went to augment the Official Switch.
Being the first public automatic exchange, Epsom attracted considerable press attention and some detailed descriptions of the technical arrangements of these two exchanges are given in the literature and are therefore not repeated here [see bibliography]. A novelty was the dialling instruction card and that given to Epsom customers had a map showing all the exchanges in the Metropolitan district, divided into three areas. Subscribers requiring connection to numbers in the central or northern area were instructed to call up 15 for a line to the city exchange (Central). They would give the number required to the operator there for connection in the normal manner.
For connection to the south-eastern district of London customers dialled 16 and were connected automatically to the operator in Croydon, while 17 seized a junction to Sutton where calls to the south-western district would be connected. The taboo on numbers starting with 1 had obviously not set in at this time. Subscribers' numbers started at 200 (or 211 if you prefer) and operator calls (enquiries and trunks) were made by dialling 0 (marked 'Long Distance' on the dial, following normal American practice).
In the two years between 1912 and the start of the Great War several further private installations of Strowger equipment were made. The ATM Company was one of the early suppliers and its first private customer was Messrs Tweedale & Smalley of Castleton, near Rochdale, who had a 100-line installation in 1913. The following year they supplied Messrs Davidson & Co. Ltd. with a system of automatic telephones throughout their Sirocco Engineering Works, Belfast. Further orders were secured for several small private installations of 25 to 100 lines and upward, for telephone intercommunication in factories, offices, collieries, etc.. In addition export contracts were won for two exchanges in the Argentine and an initial installation for the Indian government at Simla.
The British firm of Siemens Brothers had before the first world war close connections with Siemens & Halske in Germany, and their British automatic productions owed a lot to German practice. S&H acquired the German patent rights to Strowger's designs and had, in fact, applied a lot of thought towards modifications to the system. Innovations of theirs included the preselector or uniselector linefinder, which allowed economies in apparatus and the dial or exchange tone, which indicated that you were through to the exchange and that dialling could commence. Another improvement was the so-called free tone (Freizeichen in German), which indicated that the called subscriber was indeed free and not engaged.
Their installation of a 150-line capacity exchange at King's College Hospital at Denmark Hill in 1913 and a 1,000-line board at their Woolwich factory in 1914 represented thus the first two British exchanges to give ringing tone. Two other "firsts" were scored, in that these systems used German handset-type telephones (ATE supplied pedestal ("candlestick") instruments. In addition the installation in their own works was also the first PABX (private automatic branch exchange).
"As a rather special favour", the Electrical Review of February 27, 1914 reports, "the Post Office has permitted the automatic exchange to be coupled to the public exchange system, for experimental purposes. This of course necessitates the addition of a private manual exchange through which the Post Office calls are passed to the local stations, the automatic apparatus being cut out of circuit when a line is through to the Post Office. [The same principle was being provided for fifteen years later on S&H private automatic exchanges (PAXs) supplied in this country by Automatic Internal Telephones Ltd., though it was clearly not used. Dialling a 1 on these boards illuminated a lamp above the calling extension's number on a jack-strip. Subs' lines were wired through break jacks, enabling the connection of a Post Office call to release the auto equipment.]
As a footnote, it is interesting to speculate whether any other installations of automatic exchanges were made before the establishment of ATM in 1911. The Electrical Times of November 30, 1911 remarks "The British Insulated and Helsby have taken the automatic under their wing, and already one hears of two or three exchanges worked on these lines in this country." Certainly my colleague Norman Pearce, who has had an interest in telephones for many years, recalls almost acquiring some early Strowger telephones before the last war. The system was in an office in the City of London and the phones were said to have had the large "half-moon" dials. It should be noted that Siemens & Halske maintained production of this pattern of dial in Germany for some time, and the first Siemens Brothers auto installation (1914) employed dials of this kind. So "half-moon" dials do not necessarily indicate an early Automatic Electric installation, but the thought is intriguing.
Whilst the Strowger technique was the longest established system of automatic telephone switching, it was by no means the only option open to the Post Office when it decided to make its trials. Three alternatives were the Lorimer, Rotary and Betulander systems, and as we have already noted, a Lorimer system was ordered for the Caterham Valley.
There were in fact delays in providing this exchange, and it was in fact eventually installed not at Caterham, but in Hereford. It was opened on August 1, 1914, with an initial capacity for 500 lines. The manufacturer was the Canadian Machine Telephone Company of Toronto, using the technique patented by the American E.A. Faller, and known as the Lorimer system. This adopted an entirely different approach to automatic switching from that of Strowger.
The basic mechanism was a rotary switch, with a 100-point cylindrical bank, driven via electromagnetic clutches from a system of continuously rotating shafts. Each switch had ten sets of brushes or wipers, equally spaced around the shaft, any required group of ten contacts being chosen by selecting the appropriate wipers by means of a pulse-driven register switch associated with each main switch. The switches were inter-connected to form the equivalent of the classic arrangement of line-finder, group selector and final selector.
At the subscriber's end the number to be called was set up by the adjustment of four levers which also gave a visual indication of the four-digit number chosen. To start the call, the subscriber gave a single turn on a crank handle. This arrangement was claimed to be more reliable than a dial, since the subscriber could check the number selected before calling (or afterwards in the case of a wrong number), but the mechanism did of course limit future expansion on account of its fixed four-digit capacity. As things happened, Hereford performed reliably for more than eleven years, but it was always non-standard and there were no others like it in Britain.
Another automatic system employing levers to select the required number was the Betulander, though in this case up to five levers could be fitted at any time to an existing telephone (to cope with extensions to the exchange and thus to its numbering range).
G.A. Betulander was an engineer in the Swedish Post Office, who had been studying the problems of automatic telephone switching since 1900. He devised an exchange, the core of which was relays and an electromagnetic switch which operated in the vertical plane only. This gave its name to the "straight-line" system of telephony, for practically all the operations took place in straight vertical lines. The principle by which the required number was attained was that of successive selection, allowing expansion of the exchange to almost any size up to 100,000 lines.
Having set the levers on his telephone to indicate the number desired, the subscriber lifted the handset (the instruments looked quite modern) and the levers delivered trains of impulses, beginning with the highest power of ten. This movement was visible to the subscriber; another confidence booster was an audible ringing tone, which was not provided on the Strowger exchanges (naturally busy tone was returned if the wanted number was engaged). The selectors were grouped together and made contact over multiples in the form of fields of ten pairs of parallel bare wires. This arrangement reduced the number of soldered joints in the exchange significantly. Three types of selector were used, a subscriber's individual preselector (or line-finder), an appropriate number of group selectors and the final (units) selector, and the whole arrangement was highly ingenious. Between 1913 and 1914 the system was further refined and multi-contact relays were substituted for the vertical motion selectors.
Exchanges of the Betulander design were already in operation in Sweden as far back as 1903, and 1911 a company was established to exploit the system in France, where some systems were sold. In the same year it was exhibited at the London Electrical Exhibition. Commercial exploitation in Britain started in 1913, when Marconi's Wireless Telegraph Co. Ltd. acquired world-wide control of the Betulander patents outside Sweden. A demonstration exchange was established in Marconi House, London and presented to the press in May of that year. In August the Betulander Automatic Telephone Company was formed and according to Baldwin, some business was done.
Because of the war, the company's efforts were diverted to other purposes and only a few private exchanges were sold. In 1915 the firm's name was changed to the Relay Automatic Telephone Company, and subsequently that company was extremely successful in selling PABXs based on the all-relay system. A single public exchange of this type (500 lines capacity) was installed at Fleetwood in 1922.
The third machine-switching system developed before the first world war was the Rotary of the (American) Western Electric concern (Western Electric was the manufacturing arm of the Bell System). During this period the company was very active in Europe and felt the need for an automatic exchange system to sell here. Rotary had been developed by the Bell System in parallel with the Panel system. Rotary differed from the latter by using selecting switches with rotary rather than linear motion. Both Rotary and Panel differed from Strowger in that they used power-driven sequence and selecting switches controlled by revertive pulsing and also employed digit registers for the wanted number and translation. The Rotary system was developed by a group led by F.R. McBerty and was considered less favourable for Bell System use than Rotary; it was, however, thought fully adequate for use in Europe and in 1911 McBerty was sent to Western Electric's European plants to set up facilities for further development (Antwerp) and production (North Woolwich and Antwerp).
The Post Office had the distinction of acquiring the first Rotary exchange in Europe: this was a 2800 lines capacity affair initially equipped for 800 subscribers. Located in Darlington and opened on 10th October 1914, it was the first British exchange with four-digit numbers. It was followed by a smaller example at Dudley the next year. Much was found to commend the Rotary system but it was considered to be more complicated than Strowger, with which the Post Office was more familiar, and there were some misgivings about its dependence on common apparatus. Its production was not resumed in Britain after the war.
No further Rotary exchanges were bought by the BPO, but from 1923 to 1929 six exchanges were supplied to the Telephone Department of Kingston-upon-Hull. After the 1914-18 war the production facilities were moved to Antwerp; world-wide the system had considerable success and Rotary equipment manufactured in Antwerp amounted to about nine million lines by 1973.
ON ACTIVE SERVICE
The 1914-18 war profoundly disrupted the plans of the Post Office for further experimentation with new types of automatic exchange; it also impeded the efforts of Siemens Brothers to introduce their first public exchange for the Post Office. It was noted in Chapter 2 that Siemens Brothers had installed a couple of automatic internal exchanges in 1913 and 1914, and that these owed a lot to contemporary German Siemens practice. The outbreak of war must have caused this firm more problems than others, given the lack of contact with the main design department. It also meant that the opening of Siemens' first public exchange, Grimsby, was considerably delayed. While this 1,300-line exchange was substantially complete in 1916/7 (and was described in the IPOEE Journal then), it did not open until September 1918.
Although the exchange supplied by Siemens conformed to Strowger principles, it differed in many details of design. It employed open-type single-sided racks, a central motor interrupter source of pulses (rather than self-driving mechanisms), rotary preselectors (later renamed uniselectors by the BSI), and a two- motion selector which had no side switch and was controlled entirely by relays. All these features were of pure German origin. The ten-contact preselectors were used as primary and secondary uniselectors, and gave a higher call handling capacity despite the use of small capacity switches.
Another feature imported from Germany was the clear method of laying out schematic diagrams and the labelling of the lines A, B and C rather than +, _ and P. This convention and the technical features mentioned above were maintained as standard Siemens practice for many years. In the IPOEE Journal's description of Grimsby the author pays particular praise to the ingenuity of the Siemens system of drawing circuits, which long predated the adoption of this style by the Post Office and other manufacturers. Contacts are drawn detached from the coils of their relays to enable the whole of a logically related group of circuits to be shown one sheet, so that there is no need to trace a circuit through. Another benefit is that lines seldom cross.
It has already been noted that private users preceded public ones in the use of dial telephone systems, and the war served to maintain that preponderance for a number of years. Before the first world war, the Siemens company had devised small exchanges of 25 and 50-lines capacity, intended for unattended operation in villages or large establishments. The first of the private exchanges were brought into service in 1913, and the intention was that some would be used by the Post Office as public exchanges at Colnbrook, Kelvedon, Hurst and Ramsey, but the war intervened. (Two 40-line equipment's were eventually supplied, for Ramsey and Hurley, in 1921).
It was stated in the Telegraph and Telephone Journal of February 1915 that six small community exchanges were already in use in Germany and the British design followed closely the practice of the German originals. Known as nos. 1 and 2 Autophone, they are illustrated and described in the 1919 edition of Poole's Practical Telephone Handbook. The author notes that many of these were used in British munitions works during the war, where they were especially useful for all-night work without operators. Siemens own publicity also notes that a large number of automatic exchanges were supplied to government departments, munition and other controlled factories.
The ATM company was the only other in a position to supply telephone equipment during the war and supplied PAXs to War Office and Admiralty installations at Crombie (the armaments depot of Rosyth), Wylies, Rosyth, Blackbank and Port Edgar. It also continued to equip public exchanges in a number of other towns, largely with apparatus (and installation staff, known as switchmen) imported from the USA. At one exchange this led to the adoption of a sort of pseudo-Yankee jargon, which infuriated the senior supervisors. Thus the more go-ahead British staff now said 'grounded' rather than 'earthed', 'open' for 'disconnected' and 'hook-up' for 'temporary connection'. A faulty inter-switch circuit was now a 'bum link' or 'phoney trunk' and the portable telephone used by the exchange faultsmen was a 'butt-in-ski'. The test clerk became the 'wire chief' and men on switch adjustment duties were known as 'trouble-shooters'.
Other exchanges installed in this period included Chepstow (1915), with 65 lines it was the smallest installation and the first unattended exchange with remote manual board. The list continues with Newport Mon. (1915), Accrington (1915) and Blackburn (1916) the latter being the first two exchanges to have inter-dialling. Portsmouth and Paisley followed in 1916. With all these exchanges the Post Office could evaluate auto working in small and medium towns, but it had no experience yet of major ones. Leeds was chosen to be the site of its largest experiment.
Leeds, equipped for 6,600 lines with an ultimate capacity of 15,000, was one of the largest exchanges in Europe and the first in Britain to adopt five-digit subscriber numbers. Work began in 1915 and continued throughout the rest of the war period. It was finally opened on May 18, 1918.
We thus reach the end of the first twenty years of automatic exchanges, a period of considerable progress. From the earliest private installations the switching techniques had been refined to a state capable of serving satisfactorily a major conurbation.
To reach this level of development several techniques had been tested, but only the Strowger was considered to have the flexibility and simplicity suitable for British application. That the trials were considered successful is evident from a report made by the Engineer-in-Chief of the Post Office in 1925. He said "All have given, and continue to give, good service at reasonable maintenance cost."
Moreover, the Strowger system originally imported "raw" from the United States had been refined and redesigned to meet British requirements. Significant improvements had been made to the first American designs, and the start had been to the task of developing the British Post Office's own practice of engineering design. Even more significant, Britain now had an automatic telephone equipment manufacturing industry of its own, removing the early reliance on American imports and creating an export market of its own.
- Aitken W., Automatic Telephone Systems. Benn, 1922.
- Atkinson J. Telephony. Pitman, 1948.
- Baldwin F.G.C., The History of the Telephone in the United Kingdom. Chapman & Hall, 1924.
- Chapuis R.J., 100 Years of Telephone Switching. North-Holland Publishing Company (Amsterdam), 1982.
- Fagen M.D., A History of Engineering and Science in the Bell System. Bell Telephone Laboratories, 1975.
- Herbert T. and Procter W., Telephony. Pitman, 1932.
Hill R. B., Bell Laboratories Record. January 1953, page 23 and March
1953, page 95.
- Kingsbury J.E., The Telephone and Telephone Exchanges. Longmans Green, 1913.
- Lawrence J.A., Fifty Years of Automatics (in Post Office Telecommunications Journal, Autumn 1962).
- Poole J., The (Practical) Telephone Handbook. Pitman, several editions.
- Post Office Electrical Engineers' Journal. Special editions marking the 50th and 75th anniversaries of the institution, October 1956 and October 1981.
- Robertson J.H., The Story of the Telephone. Scientific Book Club, 1948.
- Smith S.F., Telephony and Telegraphy. Oxford University Press, 1978.
The first Strowger systems
- Childhood of Automatic Telephony (in Post Office Electrical Engineers' Journal, pp. 296-300, 1930).
- Journal of the Institution of Electrical Engineers, vol. xlvii p. 651.
Epsom and other early exchanges
- Daily Mail, 23rd May 1912. (Drawing of the interior of an exchange.)
- Electrical World, 15th June 1912. (Epsom, pp. 1325/6.)
- The Illustrated London News, 2nd December 1911. (Illustrated feature on p. 913.)
- Post Office Electrical Engineers Journal, July 1912. (Epsom.)
- ditto, January 1939. (Portsmouth, p.321.)
- ditto, October 1939. (Official Switch.)
- Post Office Telecommunications Journal, Summer 1964. (article by Bonnard J.A., Blackburn: The Oldest Automatic Exchange.)
- The Sphere, 2nd December 1911. (Illustrated feature on p. 197.)
- The Strowger Journal, October 1951. (Portsmouth, pp. 20-29.)
- Maclean M., Modern Electrical Engineering, vol. VI. Gresham Publishing Company. (pp. 120-148.)
- The Electrical Review, 16th May 1913. (pp. 813-6.)
- ditto, 3rd July 1914. (p. 17.)
- ditto, 10th July 1914. (pp. 44-6.)
- The Telegraph & Telephone Journal, November 1914. (Darlington, pp. 25-8)
- ditto, April 1915. (Darlington, pp. 139-141.)
- ditto, September 1917. (Dudley, pp. 158-161.)
- The Electrical Review, February 27, 1914. (Private exchanges, pp. 344-6.)
- The Post Office Electrical Engineers' Journal, April 1916/March 1917. (Grimsby, pp. 86-129.)