Abbreviated "CW" or "C-W".
"A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency. ... Continuous-wave radio was called radiotelegraphy because like the telegraph, it worked by means of a simple switch to transmit Morse code. However, instead of controlling the electricity in a cross-country wire, the switch controlled the power sent to a radio transmitter. This mode is still in common use by amateur radio operators."
In the discussion of the final flight, references to CW effectively mean "Morse code communications."
"In common usage and practice, C-W designates radiotelegraphy transmission using an unmodulated R-F carrier wave, turned on and off with a telegraph key to form the dits and dahs of Morse code. The 13-series transmitters were originally designed for voice operation only. The one aboard NR16020 was modified for C-W operation, primarily because of the requirement to operate on 500 KHz. This involved two major changes: alteration to the control circuitry; and the addition of a keying relay."
In order to hear when the CW transmitter has been keyed, the receiver must have its own tone generator that beeps when the set receives a transmission.
|A1||Continuous wave (CW)|
|A2||Modulated continuous wave (MCW)|
|A3||Voice Modulation, radiotelephone|