RADIAL BEAM VACUUM TUBE 201 



an indicator. A signal on any one or signals on any group of the 30 input 

 channels would actuate the corresponding lamp or lamps at the receiver. 

 No amplification other than that provided by the receiver tube was needed. 

 A single beam was used in each tube, the other one being rendered ineffec- 

 tive in the transmitter by m.eans of two-phase potentials applied to the 



Fig. 7. — Circular trace oscillograph of transmitted signal when 3 out of 30 channels are 



in operation. 



Fig. 8. — Linear trace oscillograph showing transmitted signal with 3 channels in operation 



2 of which are adjacent. 



suppressors in the manner described above and in the receiver by means of 

 a combination of d-c. and two-phase a-c. potentials applied to the individual 

 anodes. The potential of an anode was zero when the unwanted beam 

 arrived and at or near 200 volts at the time of passage of the operating beam. 

 The rotational frequency of the beam was sixty cycles and since both 



