Figure 8.29. The input terminal goes through a switch, S2, to one end of a resistor, not labeled. A terminal labeled Reference goes through another switch, S3, to the same end of the resistor. The other end of the resistor goes to the inverting input of an op amp. The noninverting input is grounded. A capacitor, not labeled, goes from the inverting input to the output. There is a switch, S1, in parallel with the capacitor. The output of the op amp goes to the noninverting input of what looks like an op amp but it is labeled comparator. The inverting input is grounded. The output goes to one of the inputs of a 3 input AND gate and also to a block labeled control logic. The control logic block has two outputs, one goes to another of the inputs of the AND gate and the other goes to a block labeled counter. There is another block labeled clock. The output of this block goes to the third input of the AND gate. The output of the AND gate goes to the counter. There is a graph in the upper right corner. It is voltage versus time. The voltage starts at zero and rises on a straight line. It reaches a peak after the time interval T1 has elapsed. At the end of T1 and the beginning of T2 it slopes downward more steeply than it rose and reaches zero at the end of T2. Another line starts at zero and rises at half the slope of the first and at the end of T1 is only half as high. It slopes downward with the same slope as the first line, being parallel to it. And ends at zero. T2 for the second line is half as long as T2 for the first line. End verbal description.
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