The unit comes with a free 2-day trial of ACR's Advanced Testing Services. It tests your beacon through the same Search and Rescue satellites to confirm your beacon is working perfectly and actually reaches the satellites in orbit. It took me 6 attempts to get a response from the satellite (my PLB took 3 tries). The test only sends 1 short burst and if the satellite is not in the right position or the ACR testing service is flaky, you may not get a response the first few times. IMPORTANT: I've found that after registering for the ACR Advanced Testing Service, it can take an hour or two before it become active. So it's best to wait an hour or two before testing so you don't waste your battery.The GlobalFix V4 will allow at least 84 extended tests and 120 self tests. I discovered that during the shorter self-test, a 406 MHz self-test message is still transmitted from the beacon (without gps data) and the ACR testing services will still respond to the test. For best results, you should have a clear view of the Northern and Southern sky. This is normal according to the manufacturer:Provided that you follow all the instructions on how to carry out the test correctly, the test should work. However it's important to remember that the self test only transmits ONE single burst of data up to the satellites and it is possible in some circumstances for that burst to get corrupted by atmospheric conditions and other anomalies. In an emergency your beacons transmits a burst up to the satellites EVERY 50 seconds and thus if the first burst does not get through, its highly likely that the second or third burst will. However, don't worry, your beacon will continue transmitting for at least 24 hours, so even if you are in extreme conditions, the message should get through.