The 4-port base configuration comes with internal dual-source, a reference and a test receiver at each test port without front-panel access loops. The high-source output power and the low receiver noise floor provides wide system dynamic range enabling accurate S-parameter measurements for variety of microwave passive components. With two sources, source 1 is accessible through test ports 1 and 2, and source 2 is accessible through test ports 3 and 4. Recommend Option 080.