R4 AIS Transponder System is our 4th generation design. The core of the transponder is a software defined radio, combined with a high quality built-in GPS receiver and processor. The IMO compliant Saab R4 carries type approvals from a number of countries, including EU, US Coast Guard, Russia, India, Brazil and China. It can be installed as stand-alone AIS or in combination with our R4 DGPS sensor.