DSC 400 early-warning system uses Doppler radar and digital-loop-detector technology to assess the potential threat of vehicles approaching a security checkpoint and alert guards to activate preventive measures. Continuous radar analyzes instantaneous changes in velocity of a vehicle between normal and accelerated speeds. Also warns if a hidden vehicle passes a larger vehicle and attempts an attack. Best applied to long, straight runs into a facility. Radar antennas look like surveillance cameras and can be positioned on top of guard booths or on poles. Circuitry and logic trigger the alarm panel when a preset speed is exceeded or if a vehicle attempts to circumvent a guard booth. Delta Scientific Corp., Palmdale, Calif.