Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Code letters
open-in-new
<p>Code letters or ship's call sign (or callsign) were a method of identifying ships before the introduction of modern navigation aids. Later, with the introduction of radio, code letters were also used as <a href="/facts/Call_sign/k3Y1upDl">radio call signs</a>. </p>