NOTATIONS AND SYMBOLS 



It therefore became usual to draw the coils and contacts of a relay in the 

 most convenient place on the diagram, and to associate them only by means 

 of a code of symbols. The circuit of Figure 34.1 is thus transformed into 

 that of Figure 34.2. The number within the rectangle represents the resistance 



Operate 



A. key 



p'°w g 1000 

 release g q 



Figure 34.1 Relay circuit drawn with attached-contact notation 



of the coil in ohms, while the code Ajl), for example, identifies the relay as A 

 and indicates that it has 3 contacts. Special properties (e.g. slow release or 

 high speed) of the coil are shown symbolically. The contacts are labelled 



52 

 R 



1 



A2 



B3 

 G/3 



CI 



7 



500 



500 



\B} 



A A 



e/3 



500 



t. 



Kn 



500 



A/3 



1000 g C/1 



Figure 34.2 Figure 34.1 circuit redrawn with detached-contact notation 



with the relay's code letter, and their serial number (e.g. A2, the second 

 contact set on relay A). 



The usefulness of the 'detached-contact notation' cannot be emphasized 

 too strongly. It provides a complete and convenient symbolism, and once 

 it has become famihar relay circuits are easy to follow. The perpetration 



511 



