Nonlinear functions in an analog computer

TWO BASIC types of devices for simulating arbitrary functions of a dependent variable have been developed for use with the California Institute of Technology Electric Analog Computer. One of these is a resistance device whose resistance is a function of current. It is based upon the use of germanium diode circuits which switch resistances in or out either to increase or decrease the resistance as the current increases. The other nonlinear device employs the principle of a cathode-ray tube-template-photo cell servo system which makes the cathode-ray beam follow a prescribed curve and thereby produce a voltage which is the arbitrary function of another voltage. Both of these devices can be used to represent perfectly general nonlinear impedances or amplification factors.