288 Proceedings of fndiana Academy of Science. 



varying the connections to the coil. L, and by clianging the capacity at C. 

 Two tubes or two sets of tubes are used. 1. is one or more ix)wer tubes or 

 hard tubes connected in parallel. Two iwwer tubes are shown in the figure. 

 These tubes are the oscillating tubes by means of which the energy is sent 

 out into the aerial. 2. is an ordinary receiving or amplifying tube by means 

 of which the current from the telephone transmitter, T. is amplified. The 

 transmitter, T, is connected in series with a resistance, Ri and a battery, D, 

 of two or more ordinary dry cells. The resistance Ri should have a resist- 

 ance equal to that of the transmitter, T. The variation of the current 

 thi'ough the carbon transmitter causes a A^ariation of the potential 

 difference at the terminals of the resistance, Rj. This varies the poten- 

 tial of the grid of tube. 2. and causes a coresponding variation of the current 

 of the ]>late circuit of tube. 2. This current flows through the grid leak 

 I'esistance. K. and thus modulates the amplitude of the current sent into 

 the aerial by the tubes, 1. R. should be a resistance comparable to the im- 

 pedance of tube 2. The battery K is an ordinary plate battery of 20 or 40 

 volts. H is a source of high potential, about 300 volts. 



This circuit has been tried out using an aerial of poor construction. The 

 results compare very favorable with some of the standard connections. With 

 an antennae current of 200 milliampers the voice was transmitted to a coil 

 aerial of six turns 2 meters square at a distance of one-half mile. This 

 should lead one to exiject the range should be five or ten miles with a good 

 receiving aerial. 



The resistance, Ri, was an ordinary resistance box. Ro, was made of card 

 board painted with India Ink. 



