Thanks Gary, Thanks very much for your very helpful reply. I found those 2 operators manuals and downloaded them. The Keysight website is slightly confusing as those manuals were not in the same place as the others I found. I now have some great reading to catch up on!! Morris From: Gary Chatters <gcarlistaa@garychatters.com> [...] > > I have downloaded what's there, unfortunately there's no operator's manual but I did the "Getting Started Guide" with the instrument. The prog manual might stimulate me to get GPIB up and running. > The Keysight website has eight manuals for the HP5372A, including two versions of "5372A Frequency and Time Interval Analyzer Operating Manual". Is this not what you need? There are also a Service Manual and a Programming Manual and others. [...]