By the end of the 19th century a wide range of engine governors was available commercially. These governors were of different sizes (capacity), and graphical techniques had been developed to aid the steady-state design of governors. The problem of the regulation of prime movers had apparently been solved; gross instability could now be avoided and there was as yet no commonly available means of measuring small fluctuations in speed. Engineers were concerned with improvements in mechanical construction: reduction in size, improved relay mechanisms,methods of adjusting set speed and reduction in friction. They were not, with the exception of a small group in Germany, concerned with the dynamics of the governor. But the use of the governor by scientists, by Airy for the regulation of the motion of telescopes and by Maxwell and his colleagues in an experiment to determine the ohm, stimulated investigations of the dynamic behaviour and led to the formulation of criteria for stability.

This section discusses the development of servomechanism. The servomotor arose as a consequence of Farcot's attempts to devise governors with sufficient power to operate the valves of marine engines of 500 to lOOOh.p. (400 to 800 kW). The work of Joseph Farcot represents an important step in the development of control engineering. Farcot's steering engines had been fitted to five small ships of the French Navy; these ships were also equipped, with engines for rotating the gun turrets. These engines were possibly based on the rotary servomotor.

Communication at a distance has been a long-felt need. Growth of the telegraph system was rapid; even more rapid was the growth of the telephone system, theoretical investigation of the transmission of signals along telegraph lines had been carried out by Sir William Thomson (Lord Kelvin). However, the mathematical developments had changed the climate of opinion; communications engineers in the late 1920s were beginning to talk in terms of spectra and of bandwidth, and the more mathematically minded were venturing into the realms of complex-function theory. The higher frequencies of the carrier systems resulted in increased attentuation and hence in a need for a larger number of repeaters. The solution to the repeater problem was to be found in the feedback amplifier, the foundations for the development of which were laid by the pioneers of radio communication. Thus the foundations for the development of control theory and control-systems design techniques were laid.