The Gov't buiilding I used to work in had a Spencer vacuum system-the outlets for it in the hallways-No one knew where the central vacuum unit was or if it was still there.A portable Spencer unit was used to collect cuttings from the disc recording lathes in the disc and tape recording area.The unit was used as a portable vacuum for several years-loved using it!It had a Lamb motor and a contaier with a large cloth dump bag in it for collecting the dirt.The unit Disappeared-don't know what happened to it.