Solar power frees our PTTs from the lifetime limitations of primary lithium batteries. Since these PTTs can be continually recharged with solar energy, they have the potential to run for years, making them well suited for long-term studies.

The solar-recharging and energy consumption processes are carefully controlled by an internal microprocessor to optimize power distribution and permit nighttime transmissions (as opposed to less sophisticated devices where transmissions occur only when the solar cells are exposed to light).

Latitude and longitude coordinates within ±18 m.

Altitude positions within ±22 m.

Data resolution for GPS/GSM units is detailed to 0.00001 degrees, equivalent to about 1 meter at the Earth's widest point (the equator). GPS fixes also include course, speed, HDOP, and VDOP data, as well as the number of GPS satellites.

GSM transmitters take GPS fixes at dynamically adjusting intervals that correlate to the voltage of the battery. The higher the voltage, the more frequently the transmitter will take a fix. When the battery is fully charged, a transmitter can take GPS fixes as often as once a minute. At night, transmitters will collect data at a more conservative rate, with fix intervals ranging from 0.5–4 hours. These data collection interval ranges can be modified if necessary.

GSM transmitters collect GPS positions and sensory data, even in remote areas, regardless of whether or not they are within range of the GSM mobile network. The collected dataset is then transmitted once a day via the GPRS data protocol.

If a transmitter is out of range of the GSM network, the data will remain archived until a future connection can be made. GSM transmitters can archive up to 258,000 GPS fixes for later download. (That equates to 1 GPS fix every 2 minutes for an entire year!)

Sometimes, when a transmitter is unable to make a GPRS connection through the local system, it can still make an SMS connection. When this occurs, the transmitter will send a brief SMS message containing the most recent GPS location. Once the transmitter is able to make a GPRS connection again, it will download any archived data starting with the most recent.

Data from a GPS/GSM 20-70 transmitter travels directly through the GSM system to our secure MTI server. Our server will automatically parse the data and email four output files directly to the user, typically within 10 minutes of receiving the data. These four files will be familiar to our Argos/GPS users:

• "G" File: contains the GPS coordinates of each fix, with other parameters such as speed, course, altitude, HDOP, and VDOP
  Example data
• "E" File: contains engineering data, including battery voltage, temperature, and activity
  Example data
• KML File: enables GPS positions and tracks to be viewed in Google Earth™
  Example data
• Mobile KML File: enables the most recent 400 GPS positions to be viewed in Google Earth™ on a mobile device
  Example data

Users can also sign up with Movebank at www.movebank.org and have data automatically transferred to their accounts.

Regardless of the data retrieval option, the entire transmitted dataset, will be archived safely and always made available to the user.

Our GPS/GSM 20-70 Transmitters have undergone and passed testing by an independent test laboratory to obtain PTCRB and worldwide certification (see www.ptcrb.com under "Certified Devices"). We believe we are the first and only biotelemetry company to achieve this certification for any GSM-based telemetry transmitter. Certification ensures compliance and interoperability on the worldwide GSM system.