Mk II Autosync: Automatically synchronizes the timebases using GPS or GNSS. Synchronization requires both the transmitter and receiver to be independently exposed to GPS/GNSS signals at the start of the mission and periodically (every hour or two) during the mission. Additionally, Mk II auto-sync units can operate on either of two channels, allowing two independent ROVs in the same operating area. The Mk II auto-sync unit also allows for multiple receivers to pair simultaneously with one transmitter on each channel.
Mk III: The transceiver sends an interrogation pulse to the transponder, which returns an answer pulse. Slant range is calculated from the time of flight, so no timebase synchronization is needed, and thus, the system can remain submerged indefinitely. A Mk III is more like a traditional USBL. Only one pair (Transceiver/Transponder) can operate in an area simultaneously.
The canonical operational method for both systems is for the Receiver or Transceiver to be on the top side while the Transmitter or Transponder is on the vehicle.
The Transmitter/Transponder only requires power, no computer connection is required for typical applications. The Receiver/Transceiver is connected to the computer and generates the localization data.
See more about the ROVL MK III
See more about the ROVL MK II