(United States)

Notes: These two related systems were developed after Desert Storm, which saw more US vehicular deaths to friendly fire than Iraqi action. The challenge was fairly daunting, as any system would have to be covert enough as not to reveal individual units but reliable enough to function. Additionally, it would have to be cheap enough to be fitted on thousands upon thousands of Army vehicles. Jointly referred to as BCIS (Battlefield Combat Identification System), both systems entered service in 2001.

The AN/VSC-9 is a transponder only. It is a flat plate about the size of a computer keyboard that can be fitted anywhere on any vehicle, or carried by hand. It will answer interrogations out to several thousand yards (the exact range is classified) but has a “blackout window” under 150yds to prevent enemy IEDs from targeting it.

The AN/VSX-4 adds an interrogator set. This is a small box, about the size of a VCR, with a small damage-resistant and waterproof antenna. The interrogator is triggered by the vehicle’s range finding gear and issues a “friendly”, “hostile” or “uncertain” sound so the gunner doesn’t have to remove his eyes from the sight. In only 5% of the time is an “uncertain” generated.

Obviously the United States is the only user.