The device helps you when you have two loads and only one power switch. For example, you have a combined deck/steaming light on the mast and only two wires (positive and negative) inside the mast. Smart Relay powers the first channel when you turn the power switch on, and it powers the second channel when you cycle the power switch twice in one second.
Smart Relay contains a bi-stable RT424F05 relay and uses power only when channels are switching; at all other times it consumes less than 0.5 mA. It can switch 6..16V DC loads with continuous current up to 8A and peak current of 15A (4 seconds, 10% duty rate). To switch between channels, you should cycle the power in one second. If you need to have one load constantly on and one should also be on after the fast cycling of the power, just connect the first load to the incoming power terminals and the second load to channel 2.
Picture 1. Smart Relay YDSR-01
Despite the fact that the device is waterproof, the terminals are open and sea water can cause a short circuit. Do not place the device where it can be flooded by water, gets wet in the rain or sprayed with water. Always use an electrical fuse in your circuit.
Picture 2. Electrical scheme
Resistance between the active channel terminal and VCC terminal is always zero. Smart switching is managed by a micro controller inside the device's case. High voltage (over 16V) on VCC terminal can cause permanent damage to the device.