Balanced inputs and a speaker monitor have been incorporated for operator convenience in the 3581C Selective Voltmeter. The unit covers the frequency range of 15Hz to 50kHz. The display is a 5-digit LED readout, with resolution of 1Hz and accuracy of ?3Hz. Typical stability is ?10Hz/hour, after 1 hour ?5 Hz/?C. Automatic frequency control (AFC) hold-in range is ?800Hz. Linear amplitude is 30 V to 100 nV full scale and Log is 30 dBm or dBV to -150 dBm or dBV. 50Hz to 50kHz scan width (adjustable), with sweep times of 0.1 S to 2000 S. Single or repetitive scan modes.