Figure 3 shows the block diagram of a BFSK modulator. To aid the discussion of the BFSK modulator, an example is provided. The bit stream m1(t) is the signal that will be modulated (see Fig. 4). In order to obtain the FSK modulated signal, m1(t) should be passed through the given modulator (for a binary sequence). The input signal m1(t) will be directly multiplied with the signal Acos2ᴨf1(t) as shown in Fig. 5. Note that the frequency f1 is higher than the frequency f0 simply because the part that the signal with f1 represents the high bit part. Following the lower part, the bit stream will be inverted to represent the low bit levels. The inverted bit stream m0(t) is now multiplied with Acos2ᴨf0(t) as observed in Fig. 6. These signals, m1(t)Acos2ᴨf1t and m0(t)Acos2ᴨf0t will then be fed to the summer. The output of the summer s(t), presented in Fig. 7 is the signal to be transmitted.