From Command and Conquer Wiki

The pulse scanner is an interesting piece of technology. Simple and easy to deploy, it scans the surrounding area and at the slightest hint of an object matching any recorded enemy profile, sends a distress signal to the nearby GDI forces. However, the device needs at least ten seconds to identify the registered profile, and the time can be used by the enemy to destroy the scanner, as it has no defensive weaponry installed.

Five of these were deployed near brother Marcion's headquarters in Australia.