Can you use something else in them?
The manual states: "HP Mini Data Cassettes are special, high-quality digital cassettes. Other casettes may not provide adequate reliability for storing and retrieving information..."
This sounds like HP-speak for "These casettes are the same mechanically as something else that is cheaper on the market, but we want you to use ours"
Are these the same as any other mini cassette? Especially those that go into (say) dictaphone machines?