The RLB1-DPDT-V2 is a 12v / 24c  DC powered buffered relay board. The relay features dual transistor buffered inputs which may be triggered by a positive DC voltage between 5Vdc to 24Vdc or by 0Vdc. (Inputs are provided for + or – trigger). The relay contacts may be programmed via a jumper header  for each relay pole (DPDT=2 Poles) By setting this link, either +ve or -ve can be programmed to the common of either relay pole.