ts, create the waveform s(t) = Acos (wt +0), where the input bits are stuffed in the amplitude (A). We'll start with the simplest of the ASK modulators, called Binary ASK or B-ASK for short. Figure 5.14 shows you what happens when bits 010 arrive at the B- ASK modulator. As you can see, whenever a bit 0 is input, the modulator pops out - Acos(w)t for the bit duration. Whenever a bit 1 arrives, the modulator throws out +Acos(wt) for the bit duration. Take a peek at Table 5.1 for a summary of how B- ASK works. In this table, the times iT to (i+1) T refer to the time duration of the incoming bit. Input bits Output waveform -Acoswct +Acos Wct -Acos Wct Figure 5.14 B-ASK modulator Output waveform Input bits Output waveform (shorthand form) 5o(t)=-Acos Wt, iTSt<(i+1)T s,(t)=+AcosWt, iTSt<(i+1)T (t-iT) Table 5.1 BASK (i+1)T Chapter Five Input bits Output waveform Acos Wct 3Acos Wct Figure 5.15 4-ASK modulator Next up: 4-ASK. Here, we let two bits enter the modulator at the same time. Rather than simply map bit 0 to one amplitude and bit 1 to another amplitude, we let the modulator grab two information bits at a time, SO that the modulator input is now either 00, 01, 10, or 11. The 4-ASK modulator maps each set of two bits to a waveform with a different amplitude. Sometimes pictures are easier, SO glance at Figure 5.15. Here we see the input bits are 1011. That first bit pair 10 comes into the modulator, which pops out the output waveform with amplitude A. Then bit pair 11 jumps into the modulator, and the modulator responds by throwing out the output waveform with amplitude 3A. Table 5.2 provides a summary of 4-ASK. On the left, you can see the possible two bits that can enter into the modulator. On the right are the output wave- forms, which are different for each pair of two input bits. The different modulator outputs differ only in amplitude. There's one thing to point out in this table about the times iT to (i+ T, the time duration of the output waveform. The output of a modula- tor lasts as long as the input to the