Radio age research, manufacturing, communications, broadcasting, television (1941)

zation field has been the successful development of a ver)' lightweight multi-circuit relay which is capable of simultaneously switching six different 2-ampere circuits, but weighs only about three ounces. Although still in a developmental stage, the recently unveiled RCA point-contact transistor—a tiny germa- nium crystal amplifier which will perform the functions of vacuum tubes in some applications — promises astounding developments in electronic devices. Its long life, small size, resistance to shock, lower power require- ments, and ability to function without a "w-arm-up" period make it one of the most challenging devices in any miniaturization program. A comparison of sizes is revealing. A typical minia- ture tube averages M inch in diameter and 2 inches in length. The subminiature tube is Ys inch in diameter and l^.j inches long. The point-contact transistor meas- ures only 6 10 by 3 TO by 2 TO of an inch. It consists essentially of a tiny speck of germanium in contact with two closely spaced, fine wires. The wires correspond to the terminals in a vacuum tube. One of the major probleins in any miniaturization program has been that of heat dissipation. Closely packed circuits and components give off large amounts of heat that must be carried off by efficient cooling. Usually, air cooling by means of fans has been relied upon. Since the transistor has no heated filament oper- ating in a vacuum, it does not heat up. This makes it especially desirable for use in subminiature circuits. Getting about as much attention as transistors in the Tube-socket combinations from old (left) and new walkie-talkies emphasize the rapid progress in mini- aturization of radio components. miniaturization program of RCA Victor is the use of "printed circuits." Using such circuits, engineers elimi- nate bulky wires, coils, and other parts in electronic equipment by "printing" and etching their functional equivalents on conductive foil on an insulated base. Printed circuits have been under study by the U. S. Bureau of Standards for some years, and they have been used in many of RCA's military' equipments dur- ing the past decade. A recent survey indicates that important military devices now in production make extensive use of printed wiring, while numerous in- dustrial applications are also listed. More than 112 printed wiring plates are required in the government assemblies scheduled for production. The principal physical effect of printing circuits is the reduction of electronic circuit wiring essentially to two dimensions. The eflfect is enhanced where it is possible to employ subminiature tubes and compact associated components. It then affords a degree of miniaturization unobtainable by other means. Just how much saving may be realized depends on the application. Standard electronic components are now available in such small sizes that complete amplifiers may be built into volumes of less than 1 cubic inch, and RCA has designed complete plug-in I-F amplifier units employ- ing standard components that resemble miniature vacuum tubes. The printed circuit also serves as an aid to uni- formity of production, by virtue of precise repro- ducibility of the wiring pattern, as well as reduction of assembly and inspection time and costs, and reduc- tion of line rejects. These factors, together with "dip soldering," make the process attractive, even in appli- cations where size is not important. While not all components of an electronic circuit may be printed, the practice is adaptable to conductors, resistors, capaci- tors, inductors, shields, and antennas. The development of truly diminutive electronic devices now awaits only the availability of such items as smaller microphones, transformers, speakers, and batteries. From the foregoing it will be apparent that minia- turization it still in its infancy. But its impact will shortly be felt in all phases of the electronics industr)'. Design engineers had scarcely designed miniature equipments before they were forced to turn their efforts to subminiaturization. The constant pressure of the military for smaller and smaller equipment, especially in the case of airborne equipment, is still receiving the attention of nearly every available design engineer. Commercial needs for lightweight electronic equip- ment, however, are beginning to be felt, and the coming year may see an ever-growing number of such develop- ments making the headlines. 8 RADIO AGE n,i|i|iii|i|i|i|i|i|i|imi|i|m|i|i|imi|i|i|i|i|ii