The MLS-410LH is an external audio speaker with a PTA (push to Alert) button designed to work with the intercom connection on the current VLH-3000A (not compatible with any VHF radios). When connected to the VLH-3000A the user can press the PTA button on the speaker and this will signal an alert on the VLH-3000A, notifying the user to switch to intercom mode to begin two-way communication. The MLS-410LH is designed to be either bracket mounted or flush mounted, and comes with a 1 year waterproof warranty from Standard Horizon. Flush or bracket mountCompact sizeWeather resistant6.5' Speaker CableSpeaker Impedance - 4 Ohm