Option 423 adds an internal combiner, mechanical path switches and rear panel access loops. Options 400, 419, and 080 are required.
The internal combiner combines RF signals from two sources internally, which simplify test set-ups for two-tone measurements.
The mechanical path switches and rear access loops (front access loops for the N5247A source 1 out 1 and source 2 out 1) are placed between the source and test ports, and provide alternate signal paths with signal conditioning devices or external instruments that enable additional measurements without reconnecting the device under test from the test ports.