This is the circuit board plus all parts needed for you to assemble the 8 Channel I/O (4 Relay Version). Please see the product description of the fully assembled 8 Channel I/O (4 Relay Version) for more information.

The board has four 1 amp SPDT relays and four opto-isolated inputs controlled by a DS2408 1-Wire chip. The board has an LED on each output to show when it is energized.

The onboard LM78M05 voltage regulator can supply enough current to have all 4 relays energized at once but the voltage supplied to the board should not be provided over long runs of cat5 to minimize loss in the wire.

Note: The picture is of the 8 relay version, the 4 relay version will have slightly fewer parts.