122 Telephone Systems of the Continent of Europe 



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. Ij is the local jack ; cl.d the 

 ring-off drop \p\ and / 2 tne pl u s > & the nne switch ; k { and / 2 > 

 ck\ and ck^ keys for speaking and ringing to either side. Nor- 

 mally, 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- 



