The Cospas Sarsat system uses two methods of locating a beacon.
The Satellite system is designed to locate your beacon using transmission alone. The accuracy of this fix is approximately a 5 nautical mile radius, but is typically much better.
The Ocean Signal PLB1 has a built in GPS receiver which is used to encode the position in the transmission. When the GPS has a reliable fix, usually within a few minutes, the accuracy is typically within 100 metres of your actual position.