Example: we had a set time and date and location, for meeting with them for refueling purposes. When we would get close to that longitude/latitude and we or they would pick up the other ship on radar, which we thought was our contact ship, on radar maybe 20 miles away, we would call each other by air wave contact to confirm. Many times we would get a radar bleep on the screen, and then we would call " Spitfire... Richard Lima; I believe I hold you at 090°/20 miles ; do you concur?" The Ranger would then look at their radar screens and if they saw a blip bearing 270° ( just the opposite of us and at the same distance), they would then come back and say " Richard Lima... Spitfire; I concur." We would then sail and meet for the refueling. A lot of this communication was used by using what we called the "shackle code". This was a secret code using letters instead of numbers, so that any Russian or other foreign naval ships would not know our exact position, speed, course, etc. This shackle code would change every 24 hours, at 2400 hr.. Greenwich Time. Before we would leave any port, The Commanding Officer of the ship would pick up these books personally at the Naval Base and would deliver them to the Radiomen, to be locked in a metal filing cabinet in the Radar rooms (CIC).