GPS Technology in Medical Alert Systems


GPS (Global Positioning System) is a satellite-based, location identification technology found in electronic products.

Alert1 offers two mobile medical alert systems: Kelsi mobile medical alert and Pax fall detection mobile medical alert. Now our members are protected anywhere, not just at home. 

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How GPS Medical Alert Systems Work

GPS is a constellation system of 29 earth orbiting satellites. It takes 24 satellites to provide coverage around the world. The other five satellites serve as backups. The satellite flight paths are arranged so that at any time anywhere on earth, there are always four satellites visible.

The GPS chip in your PAX medical alert receives radio signals from the four visible satellites system. It determines your location in a process called trilateration. This means the PAX calculates the time the signals traveled from the satellites using the atomic clock. Alert1 then knows how far you are from the visible satellites to get your precise location. 

How Kelsi Medical Alert Systems Work

hand holding kelsi outside

Kelsi relies on Uplink Time Difference of Arrival or U-TDOA. U-TDOA is a position-location technology for mobile phone networks.

Microprocessors in Kelsi connect with receivers in cellular towers. They pick up the signal from your Kelsi medical alert device and determine your location in a process called multilateration. This means Kelsi calculates the time it takes a signal to travel from your device to the Location Measurement Units (LMUs) on the tower. By using the timing information from multiple LMUs, Kelsi knows the mobile phone’s precise location. U-TDOA is the government's standard protocol for locating devices in the event of an emergency.  

Differences between GPS and U-TDOA technologies

Both methods of location detection are highly accurate and reliable. GPS performs well in areas with clear site lines. Because GPS waves do not penetrate buildings well, U-TDOA may outperform GPS indoors, in wooded areas and in cities with tall buildings.  

Benefits of GPS Technology

pax being held outside
  • Location Accuracy: The PAX device is one of the most accurate mobile medical alert systems on the market. We use both GPS and cellular location technology to determine the members location to within a few meters. This allows our members the security of knowing we will sent help to them quickly, regardless of whether they know their location or not.
  • New Technology Plus Trusted Processes: The beauty of the PAX mobile medical alert system is that it leverages Alert1's trusted and proven response process. When the member presses their help button, our 24/7 Emergency Monitoring Center will come on over the 2-way speaker and ask if the member needs help. From there, we will connect you with someone from your Circle of Care or 911 depending on the type of emergency. It's the same reliable emergency response we patented back in 1988, but now with the freedom to go anywhere.
  • Industry Leading Fall Detection: The Alert1 PAX device offers more protection than ever before. The PAX mobile fall detection pendant automatically senses a fall and notifies the Command Center 24/7. This lets our members continue to travel and have fun, without worrying about their safety. 
  • Affordable Prices: Alert1 has worked very hard to provide a top of the line mobile medical alert system for a great price. The system starts at only $49.95 per month.
  • Great Reviews: Alert1 members love the new PAX mobile fall detection device. The pendant has all the great benefits of our home system, but with GPS and cellular location technology for an added layer of protection. Get help anywhere you are!

GPS History

Like Cheetos or deli meats, Global Positioning System or GPS was funded by U.S. Department of Defense. The purpose was to more accurately coordinate and target locations for military purposes. During the Reagan administration, the government opened up the technology for broader public use. By the Clinton administration, civilian use outpaced military use.  Today GPS technology powers much of what we do, including the PAX mobile medical alert. 


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