Most tracking studies on Australian Fur Seals use Platform Transmitter Terminals (PTTs). PTTs have a transmitter, batteries and an antenna which are packaged in a water-proof mould.

When the PTT is out of water it transmits a unique message every minute that is detected by satellites. As a satellite passes overhead while orbiting the Earth, it might detect a PTT four or more times. The more times a satellite detects the transmitter on a single pass, the more accurately it can estimate where the seal is.

PTTs can also contain sensors that detect environmental conditions. Sensors can measure depth (using pressure), temperature and light level. The data is stored on memory chips in the PTT. Some of the data is transmitted to the satellite when the PTT transmits its’ unique code. From the depth data, scientists can find out how long and how deep the seal has been diving.