Disclaimer

Informational and educational purpose

Everything on this site is provided for general information and education. It explains how technologies worked, how they changed, and how they compare. It is not written for any individual's circumstances and should not be treated as a substitute for guidance from a qualified professional.

Not professional advice

Nothing here is professional, safety, legal, financial, or purchasing advice. Contextual conclusions such as "Better for portability" describe how kinds of technology differ in general. They are not recommendations to buy, sell, use, or avoid any product or service, and we list no prices. Decisions about what to buy or how to use a device are yours to make, using current information from the manufacturer and, where appropriate, a qualified professional.

Historical accuracy

We put real effort into accuracy, drawing on museums, libraries, archives, universities, and standards bodies, and we explain how we handle dates and numbers in our methodology. Even so, history is often uncertain, sources sometimes disagree, and errors can slip through. We do not guarantee that any page is complete, current, or free of mistakes. If you find one, please tell us through the corrections page.

Hazards of older technologies

Many of the technologies discussed here involve real hazards. Depending on the subject, they can include mains electricity, the high voltages stored in old televisions and other electronics, batteries, hot components, moving mechanical parts, fuel, and chemicals used in photography, printing, or lighting. Descriptions of how something works are explanations, not instructions.

• Do not attempt repairs, modifications, or disassembly based on what you read here.
• Do not open or service equipment that can hold a dangerous electrical charge, even when it is unplugged.
• Consult the manufacturer's documentation or a qualified technician when a device needs work.
• Handle and dispose of batteries, chemicals, and old electronics as your local rules require.

Navigation and time-critical use

Our articles about maps, compasses, sextants, and satellite positioning describe methods in general terms. They are not training material and should not be relied on for navigating in conditions where an error could be dangerous.

External links

We link to outside references to support what we write. We do not control those sites and are not responsible for their content. See the terms of use for more.

Questions

If something on the site is unclear, write to [email protected] or use the contact form.