Xiaohua: 歡迎來到這一期的詞匯小百科。Now, in this edition we’ll be talking about the word “transponder”, 應(yīng)答機. This word kept popping up when the media reports the incident of the missing Flight MH370.

John: Right. So, what happened was, there are two ways to know where a plane is. One is through regular radar. With regular radar, with primary radar, you can only tell that there is an object there. However, with so many planes in the air these days, air traffic control, both civilian and military, requires a little bit of extra information. That’s really what the transponder is there for. It has craft number, its unique ID number, and a four-digit code that can mean different things at different times. So what happened with MH370 is that at some point the transponder on the plane turned off.

XH: 飛機上的應(yīng)答機 transponder 是一種輔助通信系統(tǒng)。那么我們通常所說的radar system 雷達系統(tǒng)指的是一級雷達系統(tǒng)，它只能告訴你比如飛機的位置，但一些更具體的信息，比如飛機的高度和壓力，這就需要應(yīng)答機來發(fā)送信號告知了。

JA: And so what it does is the transponder receives a signal from the secondary radar and then it returns a squawk code with its aircraft’s position, altitude, and call-sign.

XH: Transponder 應(yīng)答機是和地面上的二級雷達 secondary radar system 一起工作的。當(dāng)?shù)孛胬走_給飛機發(fā)送雷達信號的時候，應(yīng)答機就會發(fā)出一串 4 digit squawk code，也就是一組4位的數(shù)字，這組數(shù)字可以告訴地面雷達系統(tǒng)飛機的高度以及其它一些信息。

JA: Right, and so with the squawk, the four digit code, it actually runs from 0 to 7. When we look at Flight MH370, one the strangest things is that the transponder signal just disappeared. Now, it is possible, in that squawk code, in that four-digit code, to somehow communicate that there is a problem on the plane, that’s it’s having technical problems, that it’s being hijacked, or anything else. So, basically, anything that the pilots want to communicate, not over radio, but through the transponder to air-traffic control, to anyone who can receive that signal, they can do that. But, however, with MH370, nothing like that happened. Instead, it just, turned off or disappeared or who knows?

XH: 這組4位數(shù)字實際上是8進制的數(shù)字，也就是說最小的數(shù)字是0000而最大的數(shù)字是7777.奇怪的是馬航MH370如果發(fā)生了任何故障或問題，transponder應(yīng)答機都會向地面發(fā)出特殊的信號，but in fact, nothing happened. Then the thing is, what possibilities are there that there are no signals at all from the transponder?

JA: There are some cases, in fact, where air traffic control will ask certain airplanes to turn off their transponder or perhaps just turn it to standby. This happens usually when there are many planes that are close together and so it makes it easier for the air-traffic controllers to actually identify which planes is which. But, in this case, however, with the Malaysian Airlines flight, it would seem that that would have been unnecessary for that to happen.

XH: So, the only reason maybe that either the transponder is broken, or damaged, or the pilot decided to turn it off.

JA: Exactly.

XH: 塔臺可以命令飛行員關(guān)掉應(yīng)答機或者把應(yīng)答機調(diào)在備用狀態(tài)，而在馬航的事件中，顯然塔臺沒有發(fā)出這樣的指令。那只有另外兩種可能了，一是應(yīng)答機出現(xiàn)了故障，而二則是飛行員自己關(guān)掉了應(yīng)答機。That wraps up this edition of Round Table’s Word of the Week.