Module interface:
Input section:
DC +: positive power supply (by relay voltage power supply)
DC-: connect power negative
CH: relay module signal to trigger the end (high level trigger effective)

High level and low level of meaning:

High level trigger refers to the signal trigger end (IN) had a positive voltage and the negative pole of the power supply is usually between, and the triggering end of a trigger connected with the positive pole of a power supply, when the trigger end has a positive voltage or reached the trigger voltage, the relay is attracted.

Low level trigger refers to the signal triggering voltage between the end and the negative electrode of the power supply is OV, or trigger terminal voltage lower voltage than the positive power supply voltage, low to can trigger, make the relay, is usually the cathode of the power supply and the triggering end of a trigger mode connection, so that the relay is attracted.