My book about digital logics ("Digital systems" of Ronald Tocci) provides a waveform which seems illogical to me about a transmitter circuit. This is the diagram of the circuit:
The inputs for the waveforms are [A] (0011), [B] (0110), [C] (1001), [D] (0111). However, the outputs:
At the O3, I believe it must be 1110 instead of 0111 in the picture because the LSD always comes first to Z.