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by an electro-motor supplied with current from the municipal 

 lighting mains, is employed. But the present arrangements are to 

 vanish in a few months, as soon as the company's new building is 

 ready. In May 1893 Messrs. Ericsson & Co., of Stockholm, 

 delivered a sample single-cord, parallel-jack board, manufactured 

 to the designs of Mr. J. L. W. V. Jensen, the Copenhagen Tele- 

 phone Company's chief engineer, which was put into use for the 

 trunk and other metallic circuits converging at the present central 

 station, and being found entirely satisfactory, an order was placed 

 with Messrs. Ericsson for a complete installation on the same plan 

 for (ultimate capacity) 10,200 subscribers' metallic circuits and 

 480 trunks and junctions for the new central station. The board, 

 which is equipped at present for 6,240 lines only, has been 

 delivered, and is only waiting the completion of the switch-room. 

 It presents several new features, and will be clearly understood 

 with the help of fig. 32. The main idea has been to keep only 

 one indicator in shunt across the metallic loop when two sub- 

 scribers are coupled, and this has been effected by the combined aid 

 of the jacks, the plugs, and of the special relays sr. / { and / 2 are 

 the subscribers' two lines through the multiple system ; / the test 

 wire. j*j >ni show jacks at different boards, _/" at the subscriber's 

 own board, j shows a jack with a plug inserted, causing the line 

 springs s l and s. 2 to make contact with the head and tube of the 

 plug respectively, while the test spring ts is insulated from the jack 

 and thrown into connection with the testing battery, which, in the 

 manner explained below, cuts out the subscriber's drop, //is the 

 intermediate field, sd is the subscriber's drop, also acting as a 

 ring-off drop, having a very high self-induction, sr is the sub- 

 scriber's relay, which cuts out the sd when a plug is inserted in 

 one of the jacksy'V 11 . The relay and drop are shown separate ; 

 if preferred, they may be combined. Although the armature of 

 sr is shown inserted in one of the branching wires to the drop, 

 and thus leaves the drop coils connected to one side only of the 

 loop when a connection is on, it could as easily have been placed 

 midways if the wire on the drop-magnet had been wound in two 

 halves. Experience shows, however, there is no advantage in 

 doing so, because the exceedingly small capacity of the drop does 

 not perceptibly disturb the balance of the metallic circuit, sp is 



