BELIN'S RECEIVER 119 



lie along the circumference of a circle whose centre 

 is F and radius FW. 



The top of the metal arm FR is joined to the 

 other wire of the telephone line ; the function of 

 the Belin transmitter is thus to send into the line 

 a practically continuous current which varies in 

 intensity owing to the wheel W being in contact 

 with a resistance coil whose resistance is in accord 

 with the amount of relief at each instant at the 

 stylus S. 



This varying current (continuous because the 

 rheostat strips are so close together that the wheel 

 is always in contact with two or more adjacent 

 strips) is utilised at the receiving station to form 

 a photographic image. 



For this purpose Belin employs an oscillograph 

 of the Blondel pattern, which consists of two fine 

 wires stretched across the field of a fairly powerful 

 electro -magnet. The current passes down one 

 string and up the other, not through both in the 

 same direction as in the case of Korn's string 

 shutter galvanometer ; hence, owing to the torque 

 produced, the wires (AB in the figure) twist the 

 small mirror M attached to them at the centre. 



To make the damping factor e~ kt as great 

 as possible, the moving part works in oil, but 

 though this damps down the vibrations set up owing 

 to the inflow of a sudden current, it^must necessarily 

 reduce the sensitiveness. This reduced sensi- 



