Relay pin wiring:
2 pin is connected to a control voltage, 3V, 5V, 12V, 24V control voltage is used, how much voltage pick particular, see relay identifier;
5 pin normally closed, normally open pin 4, pin 3 is the common terminal, the voltage between the pins 1 and 0 is: 3,5 turned ON voltage between the pins 1 and a respective control after the foot is turned 4,3;
Pins 1 and 2 can be controlled by the optocoupler, to form a strong electrical weak isolation;