The package contains only one device model [Opto patch - isolation coupler] the new product of our company relay module adopts Opto patch - isolation coupler, with capacitance high conduction and stable performance capability. 5ma trigger current makes its work more stable [humanized interface design] Our company's new relay module design optimizes the interface according to humanized needs: each interface can be connected directly via a connection cable, which is very convenient to use. Lights of different colors help to clearly distinguish the power indicator (green) from the 4-way relay status indicator (red). [jumper installation] in this type of relay module, high or low level can trigger the module for each path [optional working voltage] This relay module has 3 module working voltage to choose: 5V, 12V and 24V. This different type of voltage has unique advantages [fault-tolerant design] This relay module adopts a unique fault-tolerant design, with the advantage of not moving even when the control line is disconnected , which can avoid some defects