The 5383A 520 MHz Frequency Counter is designed to deliver reliable, high quality operation and covers the frequency range from 10Hz to 520MHz. Sensitivity of 25 mV rms (from 20Hz to 10MHz); 50 mV rms (from 10Hz to 50MHz). Input impedance is selectable: 1 Mohm, 40 pF or 50-ohms. Resolution direct count: 1Hz in 1 sec. Features 9-digit LED display for the resolution needed in today's applications