A rectangular housing has an electronics mounting frame shock mounted in it. The frame includes a plate and two angle members extending parallelly on opposite ends of the plate. A tray holding a controller electronics circuit board is suspended from the angles with knurled screws that can be hand fastened. A processor tray holds a processor circuit board. Spring-loaded plungers on one end of the processor tray attach the tray to flanges on the end of the plate distal from the controller tray. Hand-operable fasteners attach the other end of the processor tray to the angles overlying the controller tray. With these fasteners unscrewed, the processor tray may be pivoted upward, and a rod attached to one angle raised to stably support it, thus permitting access to the controller circuit. The controller tray may also be stably supported on top of the angles to provide access to a modular power supply beneath it. A rectangular frame extends the housing by one RETMA unit. One end of a flexible baffle is attached to the housing and the other end lies against the frame forcing air over the electronics, without transmitting housing shocks to the frame.