200 



}Tr. G. Marconi 



[June 13, 



a transformer, the secondary circuit of which is joined to the coherer 

 or detector. In order to make the tuning more marked, I place an 

 adjustable condenser across the coherer in Fig. 3. Now, in order to 

 obtain best results, it is necessary that the free period of electrical 

 oscillation of the vertical wire primary of transformer and earth con- 

 nection should be in electrical resonance with the second circuit of 

 the transformer, which includes the condenser. I stated that in 

 order to make the tuning more marked a condenser is placed across 

 the coherer. This condenser increases the capacity of the secondary 

 resonating circuit of the transformer, and in the case of a large series 



Fig. 2. 



Fig. 8. 



of comparatively feeble but properly timed electrical oscillations 

 being received, the effect of the same is summed up until the E.M.F. 

 at the terminals of the coherer is sufficient to break down its insula- 

 tion and cause a signal to be recorded. In order that the two systems, 

 transmitter and receiver, should be in tune it is necessary (if we 

 assume the resistance to be very small or negligible) that the product 

 of the capacity and inductance in all four circuits should be equal. 



It is easy to understand that if we have several stations, each 

 tuned to a different period of electrical vibration, and of which the 

 corresponding inductance and capacity at the transmitting station are 

 known, it will not be difficult to tiansmit to any one of them, without 

 danger of the message being picked up by the other stations for 

 which it is not intended. But better than this we can connect to 

 the same vertical sending wire, through connections of different 

 inductance, several differently tuned transmitters, and to the receiving 



