AUTOMATIC PRINTING EQUIPMENT 



417 



the oscillogram reproduced in Fig. 6, which shows 200- and 600-cycle 

 sine waves applied to the relay windings and the character of the 

 reversals repeated by the contacts. At these and lower frequencies 



Fig. 5 



the adjustment of the relay is sufficiently stable to permit of its being 

 operated continuously for long periods without requiring readjustment 

 or other attention. 



Apparatus of this nature is frequently installed in isolated stations 

 where materials or parts needed for making repairs cannot be obtained 

 promptly, and the climatic conditions at some of these stations often 



Fig. 6 



