He didn't realise at the time that SAGE formed an important part of America's air defence systems during the Cold War but it still made an impression.

他那个时候并不知道，半自动地面防空警备系统是冷战时期美国空中防御系统的重要组成部分，但它依然给他留下了深刻的印象。

youdao

Analysts question whether it is as stealthy as claimed and its ability to penetrate the best future air-defence systems.

分析家们怀疑其隐身能力是否有声称的那么好、有没有能力穿透未来最好的防空系统。

youdao

The embassy in Baghdad plans to hire and manage thousands of private contractors to operate helicopters and air defence systems.

ECONOMIST: Iraq and the Pentagon

The Ministry of Defence has stressed that the government has not yet decided to deploy ground-based air defence systems during the Games.

BBC: London 2012: Major Olympic security test unveiled

The suggestion from US reports is that the air strike was an attempt to prevent the Syrian authorities handing over modern air defence systems to Hezbollah fighters in Lebanon.

BBC: Analysis: Strike adds complexity to tense region