In the decade or so since control system technology was developed, great strides have been made in all fields of endeavor in applying control system concepts. While, formerly it was generally -assumed that control system technology was a part of the field of, electrical engineering, the current trend in teaching and research is toward a universal approach to the subject. This has been possible because control system ideas are truly a common denominator. The history of several types of systems is traced and it is shown that in all cases, regardless of the discipline in which the system traditionally exists, rapid progress can be made once control system technology is applied. Educational policies and trends in the United States are traced; it is the author's conclusion that better control system engineers will thus be trained by the colleges.

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The dynamic and static characteristics of steam power station was examined as a part of the tests on automatic frequency control of power systems. This paper deals with the characteristics of steam turbine governor.
The tests were performed by the frequency response method and transient response method. The greater parts of the results of the both methods tally with each other within the limits of errors.
From these testing results it has been concluded that the characteristics of governors are fully examined by the dynamic characteristic tests employing the transient response method and the static characteristic tests for dead bands and speed regulation.

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Several kinds of factor appear in the transfer function of a linear physical system. Among them, magnitude ratios and phase angles of such factors as real linear, exponential, integrating and differentiating ones, are profitably calculated by the frequency response slide rule. The attachment for the slide rule, presented here, is invented for the calculation of the quadratic factor (T²s²+2ζTs+1) for s=jω. It is a transparent sheet upon which a logarithmic scale of hyperbolic sine function and two reference lines are graduated.
Using this with the slide rule, frequency response of the quadratic factor can be calculated through three steps, and these steps are considerably simple. This attachment and the slide rule are also applicable to the non-minimum phase shift system whose transfer function is represented as (T²-s²+2ζTs+1) or (2ζTs-T²s²-1). This attachment has an essential drawback, that is, accuracy in calculating the magnitude ratio of a quadratic factor (T²-s²+2ζTs+1)decreases with absolute db value of ωT.

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A velocity servo system using D. C. tachometer generator as a velocity sensing device is analyzed, with respect to the most simple case whose differential equation for the system is of second order. Ripples involved in the output voltage of the generator is taken into consideration, whose frequencies are directly proportional to the angular velocity of the system concerned. The stability criteria are studied with respect to parametric oscillations caused by the ripple voltage.
Equation for perturbed variable is derived as to the angular velocity, neglecting periodic components of angular velocity of stationary state. The equation is transformed to the Mathieu equation, and the stability regions are expressed as functions of the system constants and ripple coefficient.
It is concluded that the instability of this sort is not likely to occur in practical cases, as far as the system concerned is approximated by the second order differential equation. It is due to the stability criteria that the system, for example, is always kept in stable state, whose relative damping coefficients greater than 0.03, if the ripple coefficent is of the order ten percent.

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The computer control in which it uses the present sampled input together with a finite number of past input and output samples to obtain the present output has been published by J. M. Salzer. Its special mode to show the finite settling time has been studied by A. R. Bergen and J. R. Ragazzini, and also it had been mentioned by R. H. Barker . This mode corresponds to the case where its rcot-locus passes through the origin of z-plane as pointed out by the au ther. But those considers response only at the sampling instants, it should not be heedlessly concluded that the mode apparently having the finite settling time is most desirable without careful study of the complete response between sampling instants.
This paper deals with the controlled area, the over shoot, and the response time correlating with the physical meaning of the computer control. As the result of the comparative study between the continuous control and the sampled-data computer control, the latter exactly has better ability than the former under certain circumstances although the latter is prove to fall into the dangerous hidden instability in a case of bad adjustment.
The computing controller which uses not only present and past samples but also the future input samples originating from the predictor, is proposed.

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