The MR221 is a miniature relay board with terminals for the Input & Output. The relay is a dual changeover. The relay contacts are rated at 2Amps. Ideal for switching equipment of a different voltage to the circuit voltage
 
 
 
Left Terminal T1 
(1) Common  
(2) Normally Closed NC
(3) Normally Open NC  
Right Terminal T2
(1) Common
(2) Normally Closed NC
(3) Normally Open NC
Terminal T3
0v = Negative or 0V 12 volts
C1 = Positive 12 volts