... how to launch a Nuclear Missile!

"Cooperative Launch" switch

Emergency War Orders
Executing a launch command was quite an involved process consisting of several steps. A launch of Minuteman Missiles could only take place with the execution of an Emergency War Order (EWO). The following is a detailed description of how such a command was executed:
1. The crew would hear the warble tone from the Primary Alerting System speakers. Each crew member would reach for his emergency action checklist binder. This binder contained laminated checklists upon which the message would be copied as well as instructions to be followed.
2. The broadcaster would then start the message which was a series of phonetic letters and numbers. The first six characters made up the preamble and would be repeated three times. The preamble told the crew which edition and page number of a non sealed authenticator to use. Once at the right page the crew would know what message checklist to use.
3. An execution message would contain the following elements of data:
a. Enable Code. These were six characters that the deputy would dial into the thumbwheel switches on the right hand side of his console. He would then throw the enable switch which would send that command to all missiles. This allowed each missile to accept a launch command if it was executed.
b. Preparatory Launch Command Alpha (PLC-A). The PLC-A was a two digit number that the deputy also dialed into another set of thumbwheel switches. Each PLC-A determined which missiles the Joint Chiefs of Staff wanted to be launched and which would be held back.
c. Authentication Values. At this point both crew members opened their locks on the red lock box. Each would remove his launch key and a sealed authenticater (they were called "cookies") They would crack the authenticators open revealing values that had to match those in the message. If the values did not match the crew had to ask for a rebroadcast of the message from the Wing Command Post. Under no circumstance would one turn keys if the discrepancy could not be resolved.
d. Execution Reference Time (ERT). If the message was properly authenticated the crew would use the ERT to compute the proper time to turn keys.
Note: It is important to keep in mind that a missile crew could complete the above steps in less then five minutes.
Special thanks to retired Lieutenant Colonel Dennis Cabrera for his detailed assistance.

source: National Park Service