Almost as soon as telegraphers began sending messages, they realized that they were sending the same messages over and over. Often, these messages were meant for other operators to facilitate the handling of messages. For example, one operator might ask another operator, “Are you ready?” meaning are you ready to receive a message. Another common message would be one asking the operator on the other end of the line to wait.
Instead of sending these messages over and over, operators developed a shorthand for common messages. To save time, they would send a number instead of the complete message. For example, the number 1 meant “Wait a minute.” “Are you ready?” was shortened to the number 6. An operator would send 134 when he or she wanted to ask, “Who is at the key?” This code was standardized in 1857, and published in that year’s National Telegraphic Review Operator’s Guide.
The Guide also defines the message 73. Today, we take this to mean “best regards,” but in those days, the literal definition was quite different from the definition we have today. In 1857, 73 meant literally, “My love to you.” Even though it stood for a flowery sentiment, telegraph operators adopted this code as a way to greet each other on the wire and to wish each other well.