Neptune Systems PM3, Dissolved Oxygen, Temperature, I/O Expansion Box. The PM3 probe module (shown above) , includes support for dissolved oxygen, temperature, and 6 digital inputs. The PM3 features are: * Monitor/Control Dissolved and temperature. * 6 digital inputs for float switches, water on floor sensors, pressure sensors, etc. * Full datalogging support in Apex Base module. * Up to 240 AquaBus modules can be added to the Apex system. * Plug and Play. Automatically recognized when installed into the system. * Two AquaBus connectors for flexible expansion via AquaBus * Comes with 3' AquaBus cable. * Galvanic Isolation for accurate and reliable probe readings. * Led Status Indicator * Upgradeable firmware. * Compatible with Apex and Apex Lite systems.