The phrase "are needed to trigger" is correct and usable in written English.
It can be used when discussing requirements or conditions necessary to initiate a process or event.
Example: "Certain conditions are needed to trigger the alarm system in case of an emergency."
Alternatives: "are required to activate" or "are essential to initiate".
But the conditions Draghi says are needed to trigger the bout of bond-buying are frequently explicitly political demands of elected governments.
Labour rules says 72 MPs – 20% of the parliamentary party – are needed to trigger a leadership election – but if more than 40 Labour MPs were to publicly call for Brown's removal, his position could become unsustainable regardless of the mechanics of an election.
So larger T 3 -values are needed to trigger shallow landslides in case of the absence of a free-face.
But researchers had already begun to suspect an additional player: HLA histocompatibility genes, whose protein products are needed to trigger immune cell activity.
PET brain imaging is sensitive enough to detect delicate changes in brain metabolism since few receptors are needed to trigger specific accumulation of the imaging agent while fMRI requires repeated trials to increase signal-to-noise ratio [23].
Interventions are needed to trigger identification and further evaluation of abnormal glucose tests.
At least 47 MPs would be needed to trigger a coup and nominate an alternative leader at party conference.
Cavani will not come cheap - a fee of 50million euros (£42million) is needed to trigger the release clause in his contract with the Serie A club.
He was watched by police and the security services as he flew into Heathrow, drove with the gang to an internet cafe and showed them an image of the device that was needed to trigger the bomb.
Neil Gallagher, an assistant director of the F.B.I., "believed that Mr. Radek's criteria for what information was needed to trigger the seeking of an independent counsel were too stringent," the report said.
