An interface receiver having multiple tiers such that a first tier in the receiver houses a module having its longest dimension in a first direction and a second tier houses a module having its longest dimension in a second direction perpendicular to the first direction. The receiver has three or more cams on each of two parallel sides. The receiver is capable of being mated with “legacy” test adapters having two pairs of parallel sides with each side in one of the pairs having two locator elements for engaging with the cams of the receiver and new test adapters of the present invention having an odd number of locator elements on each side.