“Good morning from WBAL-TV 11 News!” You might hear combinations of this introduction while listening to the radio or watching TV, but have you ever wondered where those strange letter combinations come from? Every station has its own call sign or call number that serves as a unique identifier to its specific channel. Here’s a guide to call numbers around the world.
Before we had access to thousands of channels via cable, satellite, AM, FM, XM, and the internet, there was only the telegraph. The telegraph was invented in the 1830s and was the first reliable long-distance form of communication. It used electrical signals through cables that were intercepted by a receiver. When the receiver got a signal, it made a clicking noise. Using a series of short clicks and long clicks (also known as dots and dashes), people could send messages using Morse code.
The invention revolutionized communication, but it was still time-consuming to send long messages. On average, people could only send about 13 words per minute. In a pre-cell phone and internet world, that’s pretty quick, but people were always looking for ways to make communicating more efficient.
Invention of call numbers
Call numbers were invented as a quicker way for people to identify themselves by telegraph. In 1912, a group of communications experts met at the London International Radiotelegraphic Conference and assigned every country in the world a unique set of letters for their respective radio stations. For example, if you received a telegram from call sign EBT, you’d know it was from Spain.
Many countries had call signs based on the their country name. Germany had call signs that started with a D (for Deutschland), Britain had stations that started with a B, France had F stations, and so on. Not every country received meaningful call numbers, though. The United States ended up with some of the K (from KDA to KZZ), N, and W channels. The U.S. eventually acquired the rest of the K call signs, along with some of the A signs.
Simply knowing which country a call number originates from isn’t very helpful, so after the countries were assigned their letters, individual stations were assigned two more letters to give them a unique identifier. At first, stations were assigned letters on a first-come, first-served basis. The very first radio station in the United States to register after the 1912 conference would have gotten KDA — since that was the first channel available. The next would have gotten KDB. The trend continued until there weren’t any channels left, around 1920. Once the three-letter combinations ran out, the U.S. switched to four-letter call signs to allow for more stations. These longer call signs still exist today.
Using this strategy, you could tell what country a message was coming from based on its call sign. However, some larger countries started to use call signs to be more specific about the location of a station. Since the United States had both the K and W call numbers, the Federal Communications Commission (FCC) assigned stations west of the Mississippi River with K signs and stations east of the river with W signs.
Radio call numbers on ships are reversed. Ships in the Atlantic have K call numbers, while ships in the Pacific have W call numbers. The swap allows you to tell when a radio signal is land-based and when it’s water-based. If you’re in California and get a transmission from a W call sign, you know it’s most likely from a boat.
Military vs. civilian
In addition to location, call numbers can also provide information about their senders. For example, K and W signs were given to civilian commercial stations, while A and N call numbers were assigned to the military. The letter A is for the Army and the Air Force. The letter N is for the Navy and the Coast Guard.
Modern call numbers
After the telegraph was replaced by faster, more efficient methods of communication, call signs weren’t as necessary. Many countries — especially smaller ones — decided to stop using them completely. The United States continues to use four-letter call signs as a way for the FCC to keep track of broadcasting stations around the country.
By 1922, stations could pick their own call signs — as long as they weren’t already taken. At first, the FCC retained authority to deny a request for a call sign if it was inappropriate, such as if the acronym was already being used by a government office or if it was the initials of a president. By the 1980s, however, stations were allowed to choose whatever three letters they wanted after K or W. Today, plenty of clever station call signs remain. For example, the Detroit Police Department named its station KOP.