The DC 501 100 MHz Counter measures frequency from 10 Hz to 100 MHz, and totalizes (counts number of events) from 0 to 107 at a maximum rate of 100 MHz. Seven 7-segment light-emitting diodes (LED's) provide a visual numerical display. The decimal point is automatically positioned and leading zeros (to the left of the most significant digit or decimal point) are blanked. Digit overflow is indicated by a front-panel LED. Signals to be counted can be applied via a front-panel BNC connector into an impedance of 1 MO and 20 pF or via the rear connector into an impedance of about 50 £2 and 20 pF. The DC 501 is designed to operate in a TM 500-Series Power Module only.