Talk:Swing-door operator

I am wondering if anyone know what liquid or oil is used in the hydraulic device to slow down the movement as a dash-pot. Your help is highly appreciated.

Swing-door operator operates a swing door?
A swing door is generally a double action door: going both ways. Most swing-door operators probably don't operate a swing door it seems. Only an (ordinary) single action door (hinged door). I propose to correct this.