A back-up system wold be anything that takes over in the event the main system fails. An example would be a back-up generator in case the power goes out.
A system backup is a copy of your computer data. It is usually the files you have saved on your computer but can also extend to other data such as your applications, settings, operating system and metadata.
backup
Anything redundant is a back-up system.
Hypoxic Drive
Synchronize Back-up System
because they had to back up other countries when they got in war
What Caribbean countries have a subway system?
the uk japan a LOT of countries, in fact. look up some countries on wikipedia and they should say which system they use in that country.
Anything redundant is a back-up system.
The Buddhists originally opposed the caste system but in Buddhist countries such as Japan similar systems were set up.
Countries have allies as a kind of back up when ever their country are having problems (Example War invasions) the country that has agreed to allie them have to step in to help them out. The alliance system dragged lots of countries into World War One.