ULTRA-SHORT-WAVE RADIO TELEPHONE SYSTEM 



535 



equipment to include certain features over and above the basic require- 

 ments, it is possible to reduce to a minimum the attendance necessary 

 to assure continuous operation. Further economies are effected by using 

 equipment capable of continuous operation out-of-doors. 



Since ultra-high-frequency radio circuits are normally quite stable 

 and comparatively free from noise, it is possible to omit volume regula- 

 tion and voice operated devices such as are used on transatlantic circuits 

 at a considerable saving in cost. Under this condition it is necessary, 

 however, to provide a radio transmitter of somewhat higher power 

 capacity than would be required if volume regulation were used, but the 

 cost of this additional power is small compared to the cost of the fea- 

 tures required to provide for regulated volume operation. 



CRYSTAL 



OSCILLATOR 



8.I2SMC 



FIRST 

 HARMONIC 

 GENERATOR 



SECOND 

 HARMONIC 

 GENERATOR 



FINAL FREQUENCY 



AMPLIFIERS 



NO.I N0.2 



SECOND STAGE 

 AUDIO AMPLIFIER 



310 VOLTS 1000 VOLTS 



RECTIFIERS 



RELAY TO MAKE 



STAGE OSCILLATE 



AT 1500 CYCLES 



FOR TEST 



Fig. 1 — Block schematic of ultra-short-wave transmitter. 



With unattended operation it is desirable that starting and stopping 

 both the transmitter and the receiver be separately controlled from the 

 telephone ofifice. Local testing arrangements should also be provided 

 if possible, to allow the test board operator to determine whether the 

 transmitter and receiver are operating properly. 



In order to obtain representative information on the feasibility of 

 operating an ultra-high-frequency telephone circuit on an unattended 

 basis in the telephone plant and to secure a better idea of the mechanical 

 and electrical requirements, equipment was constructed by Bell 

 Telephone Laboratories for such an installation. With the cooperation 

 of the New England Telephone and Telegraph Company this equip- 

 ment has been used to establish an experimental ultra-short-wave 



