INTRODUCTION The Keithley Model 775 Programmable Counter/Timer is a nine digit, microcomputer based, fully programmable, universal counter/timer, The Model 775 measures with high resolution the following parameters: ' * Frequency A * Frequency B * Frequency C * Period * Period Averaged * Time Intervals A B * Pulse Width (positive or negative) A The Model 775 has an 14mm (0,56 in,) LED display, The display consists of 9 digits with an additional digit for exponent The built-in interface makes the instrument fully programmable over Ore IEEE-488 bus, The Model 775 contains a programmable trigger level that allows additional flexibility in measurements over the bus (e,g. measuring rise and fall time with trigger points other than 10% and 90%). Gate time is programmed in 46 steps from 100µsec to 10sec or external from the front panel or over the bus. MODEL 776 FEATURES Dual Channel Capability—Dual channel capability with two similar channels up to 120MHz. Full Programmability—Full programmability of all functions and modes including different SRQ masks and channel selection. High Frequency Option—HF-option adds a third measurement channel for frequencies up to 1GHz, High Resolution—A 1OQMHz clock rate, along with the latest technique in frequency counting (reciprocal technique)., provides the high resolution of 8 digits/second or 1Hz out of a :100MHz input signal. Trigger Delay Channel B—This feature is important for some channel A - B time measurements, True DC Coupling—Allows the Model 775 to do channel A B time measurements, Reciprocal Technique—This counting method provides advantages over all traditional, counters from DC up to the clock frequency (1OOMHz). The constant relative resolution (8 digits/second independent of input frequency) makes it even more useful for low frequency applications.