the ring-off, sp is pulled out, and sd replaced. This practically means eight motions for each connection, viz. : 1. Depresses line key and lifts plug. 2. Tests. 3. Plugs in. 4. Depresses calling key. 5. Releases line key. 6. Replaces indicator shutter (through). 7. Plugs out. 8. Replaces indicator shutter. Twenty-six sections, each of 240 subscribers' metallic circuits, are to be fitted. Each section has space for three operators, and may be served by one, two, or three girls as required. Each operator's calling key cp is connected with a counting machine, so that the number of connections attempted to be got through may be registered. By allowing a percentage determined by experience for non-replies and repeated rings, a good idea of the volume of passing traffic is deducible. In the circuit between the generator and each operator's calling key an optical and acoustic signal is inserted which gives warning if anything is wrong with the generator or calling circuit, as well as notice of a disconnection on the subscriber's loop over which it is attempted to ring. Each operator has within reach several pairs of double cords and keys, arranged according to fig. 33, which enable her to help her neighbours if necessary. The microphone, testing and relay local circuit current will be supplied by accumulators, and the present arrangements for ringing from generators driven off the electric lighting mains will be maintained. The arrangements for the local and trunk inter-switching—a very important matter in Copenhagen-have not yet been finally matured. Fig. 33 shows Mr. Jensen's adaptation of his idea to a double-cord parallel multiple board. j is the local jack; cl.d the ring-off drop; 1 and 1⁄2 the plugs; k the line switch; k, and ką, ck, and ck, keys for speaking and ringing to either side. Normally, when, is used as answering plug, only k and ck, are brought into play. Mr. Jensen has further modified his system to act with self restoring drops. Fig. 34 shows the alterations made on the fig. 33 arrangement in order to bring this about. sd is the selfrestoring drop and cutting-out relay combined in one piece, while cl.d is the self-restoring ring-off drop without a relay. j" = Esd. lj. k FIG. 34 Pending the introduction of the metallic circuits, the subscribers are connected to the Zealand trunks through translators of the author's construction, manufactured by Messrs. L. M. Ericsson, of Stockholm. HOURS OF SERVICE The Copenhagen central station is open day and night; the suburban ones from 6 or 8 A.M. till 8 or 10 P.M., which are also about the hours of the provincial exchanges. SUBSCRIBERS' INSTRUMENTS Magneto ringers are employed, the instruments now put in being made by the Great Northern Telegraph Company of Copenhagen. Transmitters and double-pole receivers of Ericsson's make are now exclusively used. A good many of the older sets are by the Bell Manufacturing Company, Antwerp, and the Norske Elektrisk Bureau, Christiania. A peculiarity is the use of the Lorentz induction coil for the transmitters. It consists of a ring, three inches in outside diameter, of soft-iron wire, on which is wound a primary of 36 of an ohm and a secondary of 360 ohms resistance, the whole enclosed in a radially and closelywound layer of soft-iron wire of 9 mm. section. It is stated to yield better results than the ordinary coil. Certainly the speaking in Copenhagen is very good. OUTSIDE WORK (LOCAL) The wire used locally is 125 mm. bronze, supported on small double-shed porcelain insulators. There are still, however, some single-shed glass insulators, relics of the International Bell Telephone Company, in use. The Macintyre tube joint (fig. 99, Norwegian section) is employed, and is said, on the faith of many years' experience, to be quite satisfactory. When well made, the resistance of this joint is no more than that of the unjointed wire ; the twisting brings the metal in contact at many points, and the copper sheathing apparently is quite efficient in protecting these points of contact from the weather, so that the metal remains uncorroded and even bright after prolonged exposure of the joint. Mechanically, the joint is stronger than the wire. not produce better results than these, and the the soldering bolt in any form is a decided gain. Solder could. elimination of Of course the |