Personal AIS is a VHF transmitter. With AIS transmitter in the lifejacket you have a great chance of survival if you fall overboard from a boat.
The AIS transmitter starts sending automatically if you fall into the water. The signals are captured by nearby users with the AIS Rescue Rescue app. Other vessels in the vicinity without the Rescue App, with the AIS receiver will also receive notification on their chartplotter. AIS sends your emergency message at two frequencies: 161.975 MHz and 162.025 MHz. in a circumference of 4-5 nautical miles.