SYNCHRONISING 



39 



of the photograph being transmitted. The area 

 of the picture received is one quarter that of the 

 film used in transmission. 



The method of synchronising the sending and 

 receiving cylinders now requires explanation. A 

 small error in synchronisation will cause distortion 

 of the picture received, and great care is required 



Line 



To Galvanometer 



To Battery 



FlG. 18. 



to ensure its accurate adjustment. In Fig. 18 

 let us suppose that C is the cylinder of the trans- 

 mitting apparatus, and D the receiving drum. 

 There is a projecting pin on the bottom of the 

 transmitting cylinder which once in each revolu- 

 tion strikes against a contact spring, throwing 

 it away from contact with P and into contact 

 with Q. When the spring is in* contact with 

 p_during practically the whole revolution the 



