The Gould Advance OS4000 Digital Storage Oscilloscope is a versatile instrument which combines conventional 10MHz oscilloscope performance with a digital storage system, capable of storing signals up to 450kHz. The digital method of storage offers several advantages over the more common tube storage, notably the facility of pre-trigger viewing, the simultaneous viewing of a stored and a real-time display, absence of deterioration of the stored display with time, completely flicker free, low frequency performance, and the abolition of the very expensive storage tube. Careful attention to the ergonomic design allows the OS4000 to be operated in the same way as a conventional oscilloscope with the addition of the minimum number of additional controls for the storage functions.