The combination Model 4431 THRULINE® Wattmeter provides the advantage of an RF signal sample (for use with counters, oscilloscopes, spectrum analyzers, etc.) at the same time a power measurement is made. Amplitude of the RF sample is readily adjusted by a signal-coupling control knob mounted on the front of the wattmeter case. Uses the same plug-in elements as the Model 43 Wattmeter within its frequency and power ratings.