Chapter 3 _______________________________________________________________ Installation  
VAISALA_______________________________________________________________________ 41 
Selecting the Activation State of 
the Relay 
The middlemost C terminal and either one of the terminals NO/NC 
must be connected. The polarity can be freely selected. 
NO  Normally open 
C    Common relay contact 
NC  Normally closed 
 
Relay NOT activated:  C and NC outputs are closed, NO is open 
Relay IS activated:  C and NO outputs are closed, C and NC are open. 
 
NOTE 
For instructions on how to operate the relay (for example, select 
quantity for the relay output and set the relay setpoints) see section 
Operating Relays on page 93. 
 
 
Figure 24  Relay Module 
Numbers refer to Figure 24 above: 
1  =  Indication led for the relay 1 
2  =  Relay test buttons 
3  =  Flat cable pins 
4  =  Indication led for relay 2