Simple, cheap, disposable. Intended for prototyping and temporary testing of industrial instalations. NOT fit for permanent use. Zero circuit protection and reliability. 3 x optoisolated digital inputs. Option to connect to input side common ground rail. 2 x photo mosfet outputs. Option to connect to common output side common supply rail. 1 x pushbutton. Connection to Arduino pins by jumpers, so stackable. PCB footprints for 7805 and LM317 regs.