Definition
Said when a difficult situation ends abruptly, usually just before someone has to do or say something they would rather avoid.
解困，解围，解危
I was about to answer that tricky question when the phone rang; saved by the bell!
我正要回答那個棘手的問題時，電話響了；真是及時解圍！
The meeting was about to start, and I wasn't prepared with my report, but the manager postponed it, so I was saved by the bell.
會議即將開始，而我還沒準備好報告，但經理推遲了會議，所以我被及時解圍了。
The fire alarm went off just before the boss was about to ask me about my progress, it was a total 'saved by the bell' moment.
就在老闆要問我進度時，火警警報響了，完全是及時解圍的時刻。