Even way back then we had Lidar that you could point at a target and hit the trigger. It didn't emit anything until you pulled the trigger. Don't recall how far away it worked but it was further than we could ever see in the city where I worked. Put the crosshairs on your target and Bam! The signal ceased as soon as you let go of the trigger. It was enough to alert other drivers with detectors, but depending on how far away you were, it oftentimes didn't matter. And laser detectors were pretty pricey and unreliable back then, too.
Yeah those were nasty. The Valentine would alert you to laser scatter, but unless you had a car ahead of you within 50 yards or so that got zapped, YOU were the zapped one and that overly loud alert would make you poo your britches!