Velleman projects K2633 Assembly instructions - Manual (Page 6)

6
Construction & connection
7. Connection
Connect the power voltage of the relay to the 9V DC points.
This voltage needs not to be stabilised.
The connection of the loads to the relays is very simple : at the outputs the name of the contact is given.
•
C stands for the common contact.
•
NC for the contact of the inverter that is closed in rest.
•
NO for the normal open contact.
In most cases you will only use C and NO.
In order to avoid disturbances and bum-in of the contacts when switching inductive loads (motors, heavy-duty-relays, ...)
we recommend to install a VDR over the contacts.
When this should not be an adequate cure against disturbances in the control circuit, you have to place the relay print
nearby the load itself.