An electromagnetic wave with constant amplitude and frequency. This term was extended to denote a method in Wireless Telegraphy whereby the waveform to be transmitted was switched on and off, enabling a more efficient method of transmitting Morse code. In modern terms, a Type A0 wave.
CW. In referring to laser this means that the energy emitted is continuous; a CW laser can be turned on and off like a normal light bulb unlike a ruby laser which emits its energy in pulses sometimes lasting less than a fraction of a billionth of a second.
A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off. Information is carried in the varying duration of the on and off periods of the signal.