Likely the most popular IC ever made. Radio "Bankrupt Again" Shack carried them at one time. I made a delay wiper box on a 1992 S-15 biased around it one time. I was surprised it came up on here and um.. knew what it was.
https://en.wikipedia.org/wiki/555_timer_IC
I knew what a 555 was the moment it was mentioned. It is the heart and soul of nearly every timing circuit known.
Back in the very early 1980's, Car and Driver ran an article on radar, how it worked, which detectors available at that time were the most sensitive/accurate and ran several different vehicles into a typical "radar trap" on a flat, unobstructed airstrip to see how far off the most commonly used at that time police radar units locked onto a target. Results were interesting. Generally speaking, the vehicle with the largest frontal area would be locked onto farthest away (it locked onto a semi at over 1/2 mile away) but that factors such as body material or curved vs. flat body panels (vertical, near horizontal, angled) also affected radar "visiblity". They tested a pickup truck, Jeep, several different sedans, sports cars (camaro, mustang and vette) and the aforementioned semi. Results were mainly as expected but with a couple of surprises/"discoveries".
1) The Corvette was able to get the closest, under 200' away from the radar, before it was locked onto. At first the staff thought it was because of the fiberglass body and reduced (smallest) frontal area, but on further testing realized that it was due more to the fact that-
2) The RADIATOR is the primary factor (although overall frontal area does play a factor) for being locked onto! Seems a radiator's metal tubes and fins makes an IDEAL radar reflector! The Vette "walked under" the radar because the radiator, to keep the hoodline low and mean, was canted back at an angle that reflected the radar signal up and away so that it didn't return nearly as strong a signal as did say a 5.0L Ford Fairmont with a similarly sized radiaror. The flat metal front, along with the upright radiator, caused the Jeep to be locked onto a long ways off. The monstrous-sized radiator was the semi's downfall, moreso than the semi's frontal area.
3) PAINT! Metal flake/metallic and pearled paints DRAMATICALLY increased the distance that the radar could lock on. The same "stealthy" vehicle, but with metallic instead of plain solid color paint, was locked onto consistently 2-2 1/2 times farther away than the plain one! The metallic particles/flakes were SUPERB radar reflectors!
Anyhow, back to the 555 and C&D. Toward the end of the article, they talked about the (illegal) jamming of the police X-Band Kustom radar gun as a way to prevent getting a ticket vs. using a detector to alert you. They went and built not just a jammer, BUT ONE WHERE YOU COULD DIAL IN THE SPEED YOU WANTED TO SHOW UP ON THE POLICE'S RADAR UNIT! AND PRINTED THE SCHEMATIC FOR IT, TOO! It was based on sending out a signal so much stronger than the miliwatts used by the police unit, that it overrode the police unit's receiver so it thought your signal was its signal returning. The key components were a Gunn Oscillator (the source of the microwaves with a integral waveform guide) from a microwave oven, a potentiometer, a 10 watt amplifier chip and a 555 timer chip. Plus some support components (resistors, capacitors, transistors, a hobby circuit board and a build box) all available at Radio Shack at the time.
They used one of those roadside construction zone radar speed trailers to crudely calibrate the potentiometer knob position for various speeds they wanted the radar to read, so that they had like 35, 45, 55, 60, 70, etc. marked around rhe dial (remember, the National Speed Limit at that time was still 55 mph). It worked great!
The police radar gun read whatever they wanted it to. The semi coming by at 60 read 35 mph until just a few feet away! This was because the jammer's signal was 10,000 times stronger than the return echo from the police's gun. The downside was that the jammer set off detectors for miles down the road in real-life trials. They then postited that if you hooked a switching transistor to the alert output of a radar detector, you could have a jammer that turned on only in response to the presence of an incoming radar signal and thus limit falsing everybody else's detectors for miles continually.
