Introduction The 7D14 Digital Counter plug in unit is designed for use with Tektronix 7000-series Oscilloscopes equipped with readout system. The 7D14 uses the readout system to display an eight-digit readout on the CRT of the associated oscilloscope. The 7D14 will measure frequency from 0 to 525 megahertz, frequency ratio from 0 to 10s: 1 and totalize (count number of events) from 0 to 108. The 7D14 features counting capability to 525 megaherjz without prescaling, input impedance of 50 ohms or 1 megohm, blanking of all zeros to the left of the most significant digit. trigger pickoff from vertical amplifier unit (which allows simultaneous signal viewing and counting, and a trigger indicator analog CRT display to view the “shaped'' input signal.