Standardization in human cytogenetics.

A force actuated electrical switch which discriminates between forces having varying time duration. A pendulum, including a conductive wire secured at one end and fastened to a conductive bob at the other end. The pendulum is enclosed in a cylindrical insulator containing a thick viscous fluid. At the lower end of the cylinder a metal ring is positioned adjacent to the bob and surrounding it. Under normal conditions the bob remains at the center of the ring and there is no contact. When the cylinder is moved in a horizontal direction for an extended time interval, contact is made between the bob and the ring and the switch is closed.