Detailed Product Description HM-702(wired):12D.C,auto-test for malfunction,Output:relay(N.C&N.O) and sound & flash alarm; wall mounted;Alarm level: 10% of Natural gas; HM-702L(wired,low consumption):12VD.C.,auto-test malfunction,Alarm Output: relay output N.O./N.C and sound & flash alarm, low power consumption designed. Wall mounted;Alarm level: 10% of Natural gas;