Abstract: A method and apparatus for high-speed scanning of electromagnetic emission levels includes a synchronizer for synchronizing scanning of a device under test with digitizing a output video signal from a spectrum analyzer. The synchronizer can be responsive to a synchronization signal from the device under test or can generate a synchronization signal to the device under test. Methods for calibrating the level and frequency of the video output signal are provided. Once calibrated the high-speed scanning can be used to develop single probe multifrequency/time scans yielding amplitude versus frequency and time plots, and single frequency multiple probe/time scans yielding amplitude versus space and time plots.

Abstract: A closure consisting of a bifold door which is weight balanced in any given position and which, when fully opened, occupies the minimum of space. The door consists of two unequal rectangular bifold sections, the smaller of said sections being the upper section and is pivotally attached along one longitudinal side to the frame or beam at the top of the opening to be closed and the other longitudinal side is pivotally attached in an opposite pivotal direction to the lower, larger rectangular section. The lower section is connected by a system of cables and pulleys to a counterweight which applies an upward force to the bifold door which is equal to the weight or downward force of the bifold door when in a closed, or a partial or fully opened position. When fully opened, the upper rectangular section has pivoted to a position at right angles from its closed position and the lower rectangular section has pivoted 180.degree. in relation to the upper section so as to be folded directly under said upper section.