The HP 3400B is a true rms analog voltmeter that replaces in form, fit and function the HP 3400A. Specifications of the HP 3400A and HP 3400B are identical except the HP 3400B measures to 20 MHz. Six-decade frequency coverage makes the HP 3400A extremely flexible for audio and RF measurements up to 20 MHz and permits the measurement of broadband noise and fast rise-time pulses.