Electronic support measures gather intelligence through passive "listening" to electromagnetic radiations of military interest.[1] Electronic support measures can provide (1) initial detection or knowledge of foreign systems, (2) a library of technical and operational data on foreign systems, and (3) tactical combat information utilizing that library.[1] ESM collection platforms can remain electronically silent and detect and analyze RADAR transmissions beyond the RADAR detection range because of the greater power of the transmitted electromagnetic pulse with respect to a reflected echo of that pulse.[1] United States airborne ESM receivers are designated in the AN/ALR series.[1]