The 545A is a Microwave Frequency Counter is an exceptional counter at a fantastic price. Frequency in the range of 10Hz to 18.0GHz is read directly from a 12-digit LED display which is sectionalized into GHz, MHz, kHz and Hz making it easy for even unskilled operators to make measurements quickly and accurately. Time base crystal frequency is 10MHz with an aging rate of <3x10-E07 / month, 10MHz square wave (1 V p-p minimum into 50-ohms) output is available. Overall accuracy is ?(1 count + time base error). Other features include: Test function (allows for front-panel diagnostics), Sample Rate control (variable from 100 ms to 10 sec) and a Reset control (resets display to zero and initiates new reading). Three input bands are standard: Band 1 is from 10Hz to 100MHz (sensitivity of 25 mV rms) with 1 Mohm impedance (BNC); Band 2 is from 10MHz to 1.0GHz (sensitivity of -20 dBm) with 50-ohms impedance (BNC); Band 3 is from 1.0GHz to 18.0GHz (sensitivity: -30 dBm from 1.0GHz to 12.4GHz; -25 dBm from 12.4GHz to 18.0GHz) with 50-ohms impedance (TYPE N).