770 KEPORT 1891, 



towns there is already a telephone for every 200 inhabitants, the principal sup- 

 porters, after the manufacturers and merchants, being professional men, shop- 

 keepers, and householders. If telephoned to the same extent as the town named, 

 London, with its 6,600,000 inhabitants, would possess 28,000 subscribers, but 

 owing to its greater wealth and extent it is not only possible, but almost certain, 

 that eventually London will require a telephone for every 50 inhabitants, which 

 with its present population would mean 112,000 subscribers. That number would 

 only represent four times the proportion already existing in the small towns 

 named, A successful telephonic scheme for London or any large town would 

 require to comprise several essential conditions : firstly, privacy and efficient 

 speaking must be secured ; secondly, the connecting together of subscribers and 

 their subsequent disconnection, and, if required, reconnection with others, must be 

 rendered rapid and certain ; thirdly, the rates must be within the reach of small 

 shopkeepers and householders, and should not exceed 8/. per annum ; fourthly, 

 the system must be laid out so as to be capable of indefinite expansion with- 

 out the necessity of periodical reconstruction ; and lastly, the undertakers of the 

 system must have equal rights with gas and water companies to lay in their 

 conductors underground. All these requirements, excepting the fourth, have from 

 time to time severally been met and conquered, but no existing Exchange system, 

 so far, comprises them all, although technically and commercially it is perfectly 

 practicable to combine them so as to attain as nearly to perfection as possible. 

 The sanction of the Legislature to the laying of underground conductors constitutes 

 the only doubtful quantity. The Post Office has demonstrated the feasibility of 

 perfect privacy and effective speech in conjunction with a system of underground 

 wires; and the Mutual Telephone Company, in their recently-constructed Exchange 

 at Manchester, has shown that privacy, distinct speech, and rapid and certain 

 switching are quite compatible with as low a rate of subscription as 5/. per annum. 

 The only essential requirement that has not yet been demonstrated is the laying 

 out of a system so as to permit of vast and easy expansion in every direction, and 

 this, the paper shows, is a problem admitting of easy solution provided that the 

 laying of wires is made independent of private caprice. The leading feature of a 

 cheap, efficient, and easily extensible Exchange in a large town is the division, as 

 far as feasible, of the area to be telephoned into sections not exceeding a square 

 mile in extent, with some smaller ones in situations where, as in the City of 

 London, very grgat commercial activity prevails. In the centre of each section 

 will be situated a switch-room, to which the wires of the subscribers resident 

 within that square mile will be led. As some subscribers will be resident quite 

 near the switch-room and others at the maximum distance from it, it is assumed 

 that with mile squares the average length of a subscriber's line will be about a 

 quarter of a mile, and therefore cheap to construct. Each of these secondar}' 

 switch-rooms will be connected, according to the geographical configuration of the 

 town, to either one or two central switch-rooms bj' a sufficient number of junction 

 wires. Such a multiplication of switch-rooms would be impracticable with the 

 ordinary methods of switching, but a system exists which has been thoroughly 

 proved in practice during the last nine years, and which is specially applicable 

 where a very large number of subscribers has to be dealt with. By the aid of this 

 system, which is known as the ' Mann,' or a modification of it devised by the 

 author, with the switch-rooms distributed as described, the maximum time for 

 establishing a connection between two subscribers situated at the extreme opposite 

 limits of a telephone area as large as London would not exceed ten seconds. 

 The Mann switching system only requires apparatus at the switch-rooms of extreme 

 simplicity and compactness, and calls for only a minimum expenditure of labour 

 on the pai't of the operators, while it interposes no obstacles in the shape of 

 signalling electro-magnets at the intermediate switch-rooms to the freest possible 

 passage of telephonic speech. The system is consequently better adapted than any 

 other for communicating over long distances. Privacy and long-distance speaking 

 would be secured by the universal adoption of metallic circuits. Such a system 

 would afford the maximum possible telephonic efficiency, and would enable, 

 supposing it were likewise fitted in other towns, London subscribers to talk from 



