RF Explorer RFEA-1 External Lightning Arrestor [SL4]Features Low signal losses Wide range of frequency applications Reliable quality Long work expectation Arrestors are security devices for securing the transceivers from the over voltage and current induced by bolts of lightning. We strongly recommend that the arrestors are being installed in the external lightning protection system to avoid damage to your LoRa devices caused by over voltage and strong current flow induced by bolts of lightning.