OPTEX FTN detectors 862-01-FTN-RAM OPTEX FTN wireless detector 862-01-FTN-R OPTEX FTN wireless detector 862-01-FTN-R-LC OPTEX FTN wireless ready - low current detector 862-01-FTN-AM OPTEX FTN wired detector 862-01-FTN-ST OPTEX FTN wired detector 862-01-FTN-RAM-LC OPTEX FIT AM wireless ready - low current detector