Abstract :
The advantages of individual-circuit modular construction are reviewed. Armed Services opinion is quoted, indicating that more modular construction is the most important present trend. A new modular approach is introduced, and several shapevariations which were investigated, are shown. The finally-adopted "PLUS Module" standard is described as consisting of a square socketmounted top and another square plug-mounted base, tied together by two printed-wiring boards that are slotted at their center and crossed (to form a third-dimensional PLUS symbol). The advantages of using standard printed-wiring techniques and standard component Darts, are stressed. Details are discussed, including: a design for either dip or hand-soldering methods, a moisture trap solution for a 32-pin connector, heat-dissipation provisions, and epoxy-resin sealing to cope with extreme conditions of vibration and humidity. Possible constructional variations are mentioned. Commercial and economic considerations are outlined, and a break-even point is set at 20 units, as compared with hand-wired modules. The author rates the space-factor as comparable with flat plug-in printed-wiring boards that use the minimum practical spacing; and gives the standard dimensions (in a shielding can) as i 3/8 inches square and 2 3/4 inches high.\´ In conclusion, he expresses the hope that the new "PLUS Module" will help to solve some of the problems of adapting electronic equipment to modular con- struction.
