Click here to go to our main page on coaxial connectors
New for September 2018. Electrical connectors are the biggest source of failure in modern electronics. How's that mini-USB cable you purchased at the drug store working out for you?
If you are a microwave engineer, you need to know about RF connectors. And you also need to be familiar with DC connectors.
Circular connectors with multiple pins have been in use by the military since the 1930s. There are plenty of MIL specs for them, you can find the best list on Wikipedia. "Scoop-proof" designs refer to this issue: in practice, few people look at the pin-outs of connectors when they mate them, they just jam them together and expect them to work. In circular designs, someone is likely to force the two connectors together, then rotate them until they are able to push them together. Presumably, no harm will come to the connector, but in many designs, you will be "scooping" the pins as you rotate the pair, and they become bent and damaged. Scoop-proof connectors prevent this from happening.
MIL-DTL-38999 specifies several scoop-proof designs. You can find it on the US Government web site QuickSearch. Learn about MIL specs for microwaves on this Microwaves101 page.
Surely you have marveled at the longevity of Keysight test equipment, which was previously branded as Agilent and originally as Hewlett Packard. The cables that are used on power meters and other sensors have scoop-proof connectors. The tiny bump in the cable connector must mate with the gap in the ring on the power meter's connector.
This feature is often called a bayonet. Invented by the French in the17th century and named after the town of Bayonne, a bayonet is a blade attached to the muzzle of a rifle for use in hand-to-hand combat (when the enemy is too close to shoot). It had to be quick and easy to attach or remove, and it had to be very secure. Check out this civil-war era bayonet connection solution - in this case, the bump is on the rifle and must match the gap on the bayonet:
Twist and turn to lock it in!
A more-lethal form of bayonet is still encorporated in Army basic training. The U.S. Army ROTC's Pershing Rifle Society presumably banned "bayonette training" when a Queens College pledge was killed in 1977.