Evolution of Telephones 79 



number hole corresponding to the group 

 of four figures, which comprises the tele- 

 phone number of the subscriber whom it 

 is desired to engage. Then you bring each 

 of the four numbers round in turn to the 

 stop position, and then release quickly each 

 time a number is recorded upon the line. 

 If the call is effective, you hear the ring of 

 a bell; if not, you hear a steady droning 

 noise showing that your subscriber is 

 engaged. 



In the silent exchange there are tiers of 

 switches, and here, by very complicated 

 and delicate electric instruments, the con- 

 nections are made good. I should want 

 several pages to describe exactly what hap- 

 pens here, so we will push on to note what 

 is perhaps the greatest and most recent 

 development in telephony this is telephone 

 conversation with America and the Dominions . 

 Our Post Office experts have been working 

 on the problem for a very long time, and 

 now success has crowned their efforts. How 

 far-reaching such services may prove, it is 

 yet too early to say. 



