Law Enforcement Technology

AUG 2017

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Load a dozen 12-gauge rounds in its dual-tube magazines and you know the Kel-Tec ® KSG ® is one bad tactical shotgun. But chamber another, fi re and in a fraction of a second, everything else is old school. Innovation. Performance. Kel-Tec. See more at KelTecWeapons.com www.officer.com AUGUST 2017 LAW ENFORCEMENT TECHNOLOGY 9 same place as a jammer. The distin- guishing difference between the two is that jammers are always rectangular and backup cameras have a single round lens not found on jammers. How they work Jammers work by detecting the incom- ing pulses of a LASER light from the LIDAR . Most LASER jammers are extremely sensitive and do not require a direct hit to activate. Instead they are able to detect the incoming LASER light that has been refracted or reflected by moisture, debris in the air, or reflections from the target vehicle's surfaces. Most all LIDAR speed gun manufacturers utilize a fixed pulse rate between 60 pulses per second and up to 4,000 pulses per second. This makes it very easy for the jammer to detect incoming LASER because pulsed infrared signals are not a natural phe- nomenon so even the tiniest amount of pulsed energy signals the jammer that the vehicle is being targeted. Within a few milliseconds, the jammer detects the pulse timing and activates the jammers' own LASERs to fire back at the LIDAR gun with the same frequency of the detected pulses. The jammers slightly mis-time the pulses it fires to prevent the LIDAR from prop- erly measuring the time of flight of its own LASER pulses. The other reason for jammer effec- tiveness has to do with the overwhelm- ing return signal-strength coming from the jammer. Like RADAR , the LIDAR speed gun must contend with the "inverse fourth order law," where the signal strength decreases as target dis- tance increases from the transmitter. The LIDAR's LASER power decreases on its way to the target vehicle and again after it bounces off the car and heads back to the LIDAR . Because the target vehicle's LASER jammer only has to go from the jammer to the LIDAR , its energy is significantly stronger than the reflected LASER energy from the target vehicle. Effects of jamming Different brands of LIDARs vary in their response to being jammed and some will produce a visible error code when this is happening. Other LIDARs like the Kustom Signals ProLaser III may produce a different acquisition tone; while some other LIDARs may give no indication of the presence of a jamming signal. Regardless of a LIDAR's ability to detect a jamming signal, it will not display a speed to the LIDAR opera- tor until the jammer is shut off, or when pitted against cheaper jammers, "punch-through" is achieved. "Punch-through" is the point where the LIDAR is able to overcome the jammer's countermeasures. This can be caused when the LIDAR is close enough to the target vehicle that its beam is so narrow the jammer's detec- tor circuits no longer see the incoming LASER pulses. It also can be caused when the energy coming from the LIDAR's LASER beam overpowers Circle 4 on Reader Service Card

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