Dual Frequency Wireless Charging Platform (IMAGE) University of California - San Diego Caption The prototype of the dual frequency charger is a thin, rectangular box (12.5 centimeters × 8.9 centimeters) that contains two transmitter coils: an inner coil optimized to operate at a frequency of 200 kHz (orange), and an outer coil optimized to operate at 6.78 MHz (red). The prototype setup is pictured with the two receiver coils off the charging platform (top) and side by side on the platform (bottom). The transmitter coils and receiver coils are attached to green circuit boards. Credit UC San Diego Jacobs School of Engineering Usage Restrictions Please credit UC San Diego Jacobs School of Engineering License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.