Detailed Product Description HM-701-2( stand-alone):220V A.C,auto-test for malfunction,sound & flash alarm; wall ... ;Alarm level: 10% of Natural gas; HM-701-2(wired):220V A.C,auto-test for malfunction,Output:Relay(N.C ... : 10% of Natural gas;HM-701L-2(wired, low consumption):220V A.C.,auto-test malfunction,Alarm Output: relay(N.O ...