Abstract: An improved door assembly includes a door frame having a door jamb and a door having a fixed portion including a hinged side and a locking side where the hinged side of the door is hinged to the door frame. At least one of the hinged side and the locking side of the door has at least one pivotable door portion configured to pivotably move between a retracted position inside the door and an extended position that extends inside at least one complementary shaped channel within the door jamb of the door frame to interlock the door and the door frame.

Abstract: A system for monitoring moving objects, such as the flight of honeybees and other insects, using a pulsed laser light source. This system has a self-powered micro-miniaturized transmitting unit powered, in the preferred embodiment, with an array solar cells. This transmitting unit is attached to the object to be monitored. These solar cells provide current to a storage energy capacitor to produce, for example, five volts for the operation of the transmitter. In the simplest embodiment, the voltage on the capacitor operates a pulse generator to provide a pulsed energizing signal to one or more very small laser diodes. The pulsed light is then received at a receiving base station using substantially standard means which converts the light to an electrical signal for processing in a microprocessor to create the information as to the movement of the object. In the case of a unit for monitoring honeybees and other insects, the transmitting unit weighs less than 50 mg, and has a size no larger than 1.times.3.times.