Originally Posted by xfirer1guy
POP is a form of instant on. There are various forms.
POP is the radar automatically sending a signal for a very short time. It's built into the electronics. I/O is the officer only keying the "on" button when she or he is ready to get a reading. POP lasts only a fraction of a second to try to defeat detectors. I/O lasts for as long as the officer holds down the trigger. POP can be used with I/O. But they are two different things.
I/O is a (manual) technique used so that those with detectors down the road don't get early warning, since it isn't transmitting. No transmission, no alert. POP transmits but tries to blast it for so short a time (electronically controlled) that detectors won't alert. However, nearly all detectors currently do detect POP.
This is why more sensitivity in a detector counts. It can pick up the I/O shot if there is traffic far ahead of you. How far depends on how sensitive the detector is. Cheaper detectors can't pick up radar as far ahead and so it may miss the I/O shot for traffic far ahead, but then when you become in range it will alert; however by then it is too late.
But if you're the only one on the road and there is no traffic ahead (or too far ahead for any detector) then, as they say, you're toast.