Alternative to AM and FM transmitting for data transmission?
What you describe is called On-Off Keying.

It is an extreme version of Amplitude Shift Keying where the carrier is completely off for one value.

This is the technical name for what happens when morse code is sent by a radio operator. 

Wikipedia has more information on the pros and cons:


  OOK is more spectrally efficient than frequency-shift keying, but more sensitive to noise when using a regenerative receiver