Abstract: The present technology may be directed a system for determining an angle and distance between a positioning node and secondary device using a plurality of acoustic transmitters to transmit acoustic ranging signals that are modulated using ranging sequences, respectively. The system includes an acoustic receiver to detect the acoustic ranging signals, and a signal processor to calculate times of arrival and a plurality of aliased angles of arrival of the acoustic ranging signals. An anti-aliasing module may select an angle of arrival from the calculated plurality of aliased angles using the times of arrival of the acoustic ranging signals. A time of flight may be calculated from a comparison of times of arrival for radio signals and the acoustic signals. The time of flight may be used to calculate the distance between the positioning node and secondary device.

Abstract: A concealed safety light is described where the light source is integrated and mounted into a switch or power outlet wiring device form factor (20,21,22) to replace conventional electric wiring devices. The light source (10) is controlled by a power and control circuit (90, 790) that derives power from the primary power supply or an alternate power supply. The circuit can detect light levels and turn on the light source when it is dark and also detect power failures to turn on the safety light in the event of a power failure using the alternate power supply The safety light is also capable of responding to an alarm condition from other systems. The resulting safety light is conceyaled in a standard wiring junction box and trimmed with a wall cover plate in the same way as conventional electric wiring devices, allowing it to be concealed while in plain view and provide safety lighting in a variety of ways including power failure, night light and alarm conditions.