A NEW TELEPHOTOGRAPH SYSTEM 



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two bays of relay-rack-mounted apparatus, and a cabinet of power 

 supply equipment. A third bay comprising loop terminating arrange- 

 ments, telephone, and loud speaker equipment may be furnished by 

 the telephone company if ordered by the customer. This telephoto- 

 graph equipment connected by suitable circuits will transmit pictures 

 and other forms of graphic information from point to point or from 

 one to a number of points simultaneously. 



Figure 4 is a schematic diagram illustrating the functional relation- 

 ships of the various units of this equipment. Certain features of 

 these units that may be of special interest have been selected for 

 description in the following. 



Motor and? Associated Speed Control Circuit 

 Although the driving motor for the telephotograph machine is 

 essentially of the d-c. shunt type, it functions in combination with its 

 associated speed control equipment as a synchronous unit and upon 

 starting locks automatically in synchronism with the frequency 

 generated by the local carrier and motor control oscillator. This is 

 accomplished in a manner similar to that previously used in television 

 equipment demonstrated by the Bell System.^- ^ An inductor type 

 generator built into the frame of the motor delivers an a-c. output of 

 300 cycles per second at the normal speed of the motor, 100 r.p.m. 

 The output of the generator is impressed upon the plates of two 

 vacuum tubes the grids of which are energized by the 300-cycle 

 output of the carrier and motor control oscillator as shown in Fig. 5. 



FIELD 



~ 24 VOLTS 



Fig. 5 — Telephotograph niacliinc motor control circuit. 



