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The BWD 845 is a high performance, portable variable persistence, storage oscilloscope. It incorporates a delayed, mixed or delayed trigger time base, vertical amplifiers with a ImV sensitivity on both channels and can be powered by AC, DC or an optional battery pack. The variable persistence/storage facility enables the user to view and measure intermittent signals and transients that cannot be detected on a normal Oscilloscope. It also retains wave forms at very slow sweep speeds allowing the entire waveform to be viewed rather than a moving dot. If persistence is adjusted to overlap traces, fast signals at low repetition rates can be integrated to make, them readily visible;. This technique makes it possible to view and store signals that are faster than the CRT writing rate, in fact up to 30MHz. Storage oscilloscopes are more complex than non-store models, so several features have been incorporated to simplify the comprehensive facilities provided. A standard feature of all BWD oscilloscopes is the ALL BUTTONS OUT condition for normal operation. This is incorporated in the BWD 845 and is a major contribution in simplifying operation. An AUTO ERASE cycle eases the task of setting Up the CRT controls in the storage mode. View time is approximately 4 seconds after each writing sweep is completed. It is then erased to await the next sweep. In the CHOP mode two tracés müy be written and viewed simultaneously or alternately in the ALT mode. This mode may also be used for viewing repetitive single shot signals that contain non-repetîtîve waveforms. When a long waiting time occurs before a signal is received to trigger the time base and write a stored display the screen may fade green all over. An AUTO STORE facility in the BWD 845 eliminates this problem by holding the CRT in the erase condition until the time base is triggered by a signal, thus extending the pre-trigger period to hours instead of minutes. It then automatically switches to store and a LED indicator signifies this condition. The CRT characteristics themselves form the major control on writing speed and storage. It has a burn resistant screen and operates at 7.510/ EHT to provide a well focused trace in all operating modes. To optimise its operation for both fast writing and long viewing/storage times, two switch selectable settings are provided - slow or fast. By writing in fast then switching to the lower intensity slow condition, storage or viewing times can be greatly extended. The backing electrode is also adjustable over a limited range by the front panel background control for best signal to background contrast. The combination of these wide range storage and Oscilloscope functions make the BWD 845 a very powerful tool for a wide range of measurement and analysis.