Amplitude-Shift Keying (ASK) We will add carrier waves into the modulation scheme. ASK is the simplest modulation technique. ASK is modulated over the carrier's amplitude, similar to the amplitude modulation for analog modulation. Binary transmission: we require two waveforms and . If the transmitted symbol is “1”, is used over the signaling interval . If the transmitted symbol is “0”, is used over the signaling interval . Assume the probabilities of transmitting a “1" and a “0" are equal. The transmitted signal s(t) can be expressed as for (5.2-3) ASK is often referred to as on-off keying. Fig. 5.2-1(a) gives a transmitted waveform resulting from the digital transmission of “1001101”, where Hz, and sec.