The ALT-70V-50 volume control is designed to add local or zone volume control to any 70V audio system.  The removable screw-down speaker connector accepts up to 12ga wire and the 11 steps of attenuation with make-before-break connections means that you’ll always have smooth control over the system volume.  It can be used with both 25V and 100V systems as long as the total power does not exceed 50 watts.