One known issue: The light for Channel A doesn't turn on, but the channel functions perfectly.

To use this Clear - Com RM - 400A Four - Channel Remote Communication Station, simply connect it to your existing system. When using, don't be alarmed if the light on Channel A doesn't come on, as the channel still works well. For maintenance, keep it in a dry and clean place. Avoid exposing it to extreme temperatures or humidity. If you encounter other problems, contact the customer service team.