Vac line from ALDA

[sjh]

w124 '90 300D 2.5L Turbo - Automatic.

I believe this is present on most 123, 124 & 126s but I know it is on my car.

There is a black plastic vacuum (or could be pressure) line from the ALDA that goes through the firewall. Where does this line end up? What's it do?

Thanks.