free-pendulum clock (=Shortt clock)

“Master Backup Slave” architecture

1+1 backup

4%Cr backup roll

active backup line

adaptive fault-tolerant backup

analog backup unit

and Redundancy backup

anti-disaster backup

application backup

Archive Backup

Asynchronous Backup

Asynchronous Dial-up Backup

auto backup power switching unit

Auto-backup

automatic backup

automatic backup power supply switching

automatic backup power supply switching device

automatic backup power system