[Heathkit] Question from Non-Ham

[Miles Anderson]

SK started out as one of the procedure signals sent by Morse operators
handling message traffic. In the early days of radio, this would take the
form of a ship sending a series of messages to a coastal station or vice
versa. In the heyday of transatlantic passenger shipping during the 1920s
this might amount to a dozen or so messages sent one after the other.

(By the way, all of these signs are sent as though the SK were a single
Morse letter with no character space in between ***-*-. When hand written
these "pro signs" are written as capital letters with a bar across the top.)

At the beginning of each message in the series, the transmitting operator
would send BT (beginning text), followed by the text of the message. At the
end of the message, the op would send AR (end message). When the
transmitting op had passed his or her last outgoing message, the
transmitting op would send SK (end of work or end of traffic), clearing the
receiving station to handle traffic from another ship.

Ironically, there is probably a "better" pro sign to use for a deceased
operator. That would be CL (closing station or ceasing operation), but the
coincidence that SK could be read to stand for Silent Key prevailed.

 Miles Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, NY 11963