Adjoining the central hall are the phonogram and the tube switch rooms. The former is set apart for telephone telegram business, and by its means telephone subscribers may speak direct into the head telegraph office. In this way they can dictate telegrams by telephone for subsequent transmission by telegraph. Telegrams are also sent in the opposite direction to certain subscribers who desire to receive their telegrams by telephone instead of by hand delivery from the nearest delivery office. The telephone circuits connecting the Post Office Savings Bank at West Kensington with St. Martin's le Grand, and used in connection with Savings Bank withdrawal telegrams, are also situated in this room.
In the tube switch room are placed circuits which enable telegrams received by pneumatic tube from the various branch offices to be signalled to officers in the Metropolitan District through the medium of the inter-communication switch which I shall mention later on. It also allows for the reception of telegrams originating at offices of the Metropolitan District intended for delivery from those offices connected to the Central Telegraph Office by tube.
The counter and delivery rooms are also on this floor.
The first floor, with the exception of one large room used as the telegraph school of instruction, is mainly occupied with the offices of the engineer-in-chief and his staff and the chief medical officer and his staff.
The second floor provides for the telegraph administrative offices, the cable room, and for wires working to provincial offices.
The third floor is devoted to the large central gallery and its wings, and here are placed the greater number of the provincial circuits. In addition the wires set apart for news working and for special events, to grand stands at race-courses, &c., are located here.
The Metropolitan and Home District circuits are on the fourth floor.
Now in order to combine the various floors so as to form practically one immense gallery, it is of course necessary that there should be a rapid means of communication between them. This is provided for by an extensive system of pneumatic house tubes, which makes it possible for telegrams to be circulated from point to point in the various galleries. For instance, it is assumed that a telegram is handed in at the Fenchurch Street branch office for transmission to Birmingham. This would in the first instance reach the tube hall on the ground floor by pneumatic tube. It would then be placed on the sorting table and taken to the tube connected with the central circulation table in the provincial gallery on the third floor. On arrival there it would be further sorted and taken to the section in which the Birmingham circuits are placed, and take its turn with other messages awaiting transmission to that town.
The area of each floor is so great that it is essential that the various circulation tables at particular points thereon should be directly connected by tube, thus allowing of the rapid transit of the traffic and preventing the confusion which would attend carriage by hand from point to point. In all sixty-eight house pneumatic tubes are worked throughout the day. In addition, continuous aerial cord carriers worked by electric motors are used for the conveyance of telegrams.
For the purposes of circulation, and for staffing and effective supervision, the three floors or galleries are divided into sections or divisions. For instance, the provincial galleries are composed of seven divisions, named respectively A to G, and the various circuits are grouped as geographically as possible in these divisions. The A Division embraces such south-easterly and south-westerly towns as Dover, Folkestone, Brighton, Bournemouth, Basingstoke, and Ventnor, and so on. In addition to these divisions there are the News Division, the Special Section, and the Intelligence Section. The former contains the news circuits over which press work is disseminated throughout the Kingdom. The apparatus in use for this class of traffic is the Wheatstone Automatic, which in the course of years has been so improved that whereas in 1870 it was only capable of transmitting some 80 or 100 words per minute, it is now possible, given good wire conditions, to attain a speed of 400 words per minute, although for working purposes it is not usual to exceed an average speed of from 200 to 250. This system is specially adapted for the transmission of general news, one batch of which, on specially prepared slips, is often forwarded to many different towns. A large proportion of this particular traffic is classified, being news of general interest, and is handed to the Department by the different news agencies, such as the Press Association, the Central News, the Exchange Telegraph Company, &c., for dissemination to the various subscribers in different towns.