CW transmitters are simple, inexpensive, and the transmitted CW signal doesn't occupy much frequency space (usually much less than 500 Hz). However, the CW signals will be difficult to hear on a normal AM receiver; you'll just hear the faint quieting of the background noise as the CW signals are transmitted. To overcome this problem, shortwave and ham radio receivers include a beat frequency oscillator (BFO) circuit. The BFO circuit produces an internally-generated second carrier that "beats" against the received CW signal, producing an audible tone that turns on and off in step with the received CW signal. This is how Morse code signals are received on shortwave.

Click here and  here for a history and background of Morse Code

Click here for a brief history and explanation of the Q-codes (introduced in 1931, at least 254 codes in use!)

Click here for a list of the many other abbreviations used in Morse telegraphy (and other no-voice modes as well)

"Codes of the World", deNeuf, Walters, Anderson, Folkman, Dickow, Mundt, Geisel, Cady, Cookson, Williams, Miller, pp. 102-110 in "Ports O' Call: a book of the wireless pioneers", Vol. 4, 1976, Society Of Wireless Pioneers (SOWP), 112 pp.