Fire Alarm Systems | FLM‑420‑RLV8‑S Octo-relay Interface Module Low Voltage The FLM‑420‑RLV8‑S Octo-relay Interface Module Low Voltage features eight changeover contact relays for providing potential-free output contacts. It is a 2‑wire LSN element. When connected to the fire panels FPA‑5000 and FPA‑1200, the interface module offers the enhanced functionality of LSN improved technology.