Abstract: A beta radiation particle detector having a housing that is substantially impervious to beta radiation particles and which surroundingly encompasses an ionization chamber which is defined by electrically conductive walls is disclosed. The walls terminate in an edge which defines an opening into the ionization chamber with the opening being covered by a beta radiation pervious electrically conductive window that entraps, within the ionization chamber, a quantity of gaseous molecules which are adapted to ionize upon impact with a beta radiation particle. An electrode is disposed within the ionization chamber and has a generally shallow concave surface having a width which is substantially greater than its depth and which faces the electrically conductive window.

Abstract: An automatic mat-activated operating system for swinging doors provides approach circuitry for opening the doors when an approach mat at the entrance side of the doorway is activated and override safety circuitry for stopping door opening movement and returning the doors to a closed position when a safety mat at the exit side of the doorway is activated within a predetermined initial range of door movement but not thereafter and also for preventing door opening movement if the safety mat is already activated at the time of initial activation of the approach mat. The control system thus protects pedestrians at the exit side of the doorway from being struck by the doors during their initial opening movement which may not be readily recognizable and avoidable and also protects pedestrians entering the doorway from the entrance side from being struck by unexpected return movement of the doors.

Abstract: A solid state integrated regulating circuitry for incorporation in the conventional control circuitry of automatic sliding door systems includes timing and processing circuits operative through plural inverters to deliver enabling and disenabling electrical signals to the control circuitry when the elapsed time between cycles of door opening and closing actuations are greater or less than a predetermined time respectively either to prematurely terminate or to have no altering effect upon door opening actuation, thereby to open the doors to a reduced width during low traffic conditions and to open the doors to a full width during high traffic conditions.