How to import RXJS types for TypeScript

If I understand correctly, rxjs (version 5) is written in typescript and is packaged with all the definitions.

I tried using them, but I cannot seem to find a way to do that. I get the error

error TS2304: Cannot find name 'Observable'

Here is my tsconfg.json

{
  "compilerOptions": {
    "target": "es2016",
    "strict": true
  },
  "exclude": [ "node_modules" ]
}

and the file I try to compile

const { Observable } = require("@reactivex/rxjs")

function timer(time: Number): Observable {
  return Observable.timer(time)
}

I run node_modules/.bin/tsc test.ts

Am I missing some typescript config here? Is there something to do to enable types?