Abstract: A perimeter alarm apparatus includes a loop of wire to be placed around an area to be guarded and electrical circuitry connected with the loop for detecting the absence of a signal imposed on the loop. The signal imposed on the loop is produced by a sending unit worn by a child, for example, who is intended to remain within the area bounded by the loop. As long as the child is within the area, the sending unit will induce a signal on the loop, but when the child moves beyond the loop a predetermined distance, no signal is imposed on the loop, with the result that an alarm is sounded by the circuitry.

Abstract: An alarm apparatus which is activated upon immersion. The apparatus is adapted to be worn whenever the wearer is expected to be in the proximity of a body of open water and will sound an alarm should that wearer fall into the water. The apparatus is portable, self-contained and has a water activated release to automatically release the apparatus from the wearer upon immersion of the device. The alarm is mounted in a buoyant housing so that housing is self-righting to float to the surface of the water in an upright orientation so the alarm signal is emitted outwardly of the water when the housing reaches the surface. Various embodiments and actuating and release circuits are also disclosed.