The case for combined analog-digital simulation

Abstract

The idea of combining the good features of both analog and digital devices is certainly not a new one. Numerous examples can be found in history dating back to the ancients who kept time by a slowly burning cord with equally spaced knots tied in it. Each time a knot burned, this fact was tallied (digitally) and the subintervals were estimated by interpolation (analog). One more recent example is the odometer on all automobiles where the whole miles are given digitally while the tenths are estimated on a nonquantized analog-dial wheel. Another example appears in many digital clocks where the hours and minutes are given digitally on dials, but where the seconds are estimated on a continuous analog-scale wheel. Often in determining areas enclosed by curves, a combination of digital and analog methods are used. For example, the largest possible portion of the area may be blocked out as a rectangle whose dimensions are digitally determinable and its area computed by forming the digital product of its dimensions. Then the remaining area or areas are estimated by using a planimeter, an analog device.