Anything used to detect motion will have some sort of frequency emission..... in other words, your detector sensing the bank or any grocery store with automatic doors is normal. They use what is essentially low frequency radar, so yes your detector will see that. Now, if you drive by a cop and you don't get a reading, that's one of two possibilities: he either doesn't have his radar gun on, or he has LASER..... and if he has LASER, you're toast.