The Ratelco 120‑2712‑01 IC‑9 is a weather‑proof mobile intercom unit used in industrial and firefighting applications, providing two‑way voice communication between a master station and remote mobile units. Common failure points for this class of equipment include degraded speaker or horn contacts, blown input/output protection diodes on the audio amplifier board, and corrosion or loose connections in the RF/ANT connector due to harsh environmental exposure. First‑check diagnostics: verify that the unit receives proper 24 V DC power and that the indicator LEDs display normal status; inspect the audio output path for visible damage or burnt components; and test the intercom’s wireless link by attempting a call to a known working master station while checking RF antenna continuity.[oss-gpt-20b]