Industrial Electronic Developments in the Last Two Decades and a Glimpse into the Future

During the past two decades significant improvements have been made in all types of electron tubes. Small tubes became still smaller, and the output of large tubes has been increased. Greater reliability has been achieved, and frequency limits have been extended upward. Hydrogen thyratrons have been developed, providing high power for pulse work. Ignitron ratings have been increased significantly. The problem of shutting off gas tubes by grid control has received attention and has led to two new types of tubes which at this time have, however, only limited output. To the list of photosensitive devices have been added the leadsulfide and similar cells, providing means of detecting infrared radiation of long wave length. A host of ingenious transducers has extended the use of electron tubes in the measurement and control field; smaller magnitudes of physical quantities, such as distance, pressure and magnetic field intensity can be observed and recorded. On the other end of the scale, tubes have provided HF power for induction and dielectric heating. But by far the most outstanding development of the last 15 years has been in the field of solid state or semiconductor devices. Here the transistor, announced in 1948, occupies first place, and improvements in its characteristics are coming at a breath-taking pace. In 1957 the silicon-controlled rectifier, aptly called a solid-state thyratron, joined the march. These two devices are giving industrial electronics a tremendous new drive.