Revolving door

Revolving door Wikipedia facts

Origins:
- created in Germany around 1881
- original name was Tür ohne Luftzug ("door without draft of air")

Motivations and advantages:
- noiseless;
- prevents the entrance of wind, snow, rain or dust;
- no possibility of collision, and yet persons can pass both in and
out at the same time;
- cannot be blown open by the wind;
- excludes noises of the street.

And that concludes our lesson for today.