The diagram below shows a generic communications system consisting of a digitizer and a multiplexor. For this system there are four choices for the digitizer and the multiplexor; compatible combinations (i.e. -- one digitizer choice paired with one modulator choice) of these are needed to allow the input signal to be successfully transmitted on the output channel. Some of these work, some don't. From the choices below, pick ALL the pairs that do NOT work together.

Possible Digitizer settings: 1. - PCM (8,000 samples/sec, 8 bit quantization) --; 2 - PCM (8,000 samples/sec, 4 bit quantization) 3. - Delta (16,000 samples/sec, 1 bit step size) 4. - Delta (64,000 samples/sec, 2 bit step size) OUTPUT Channel B 20-kHz INPUT Signal INPUT DIGITIZER MODULATOR Possible Modulator.settings: W. BPSK Modulation X QPSK Modulation Y. 8-level PSK Modulation Z -16-QAM O A. Digitizer #2 and Modulator" O B. Digitizer #1 and Modulator C. Digitizer #2 and Modulator 'Y 0 D. Digitizer #4 and Modulator "Z" O E. Digitizer #1 and Modulator 'W' F. Digitizer #4 and Modulator 'W