Based on switched mode technology and PWM control. Switching frequency: 25 KHz Compact and lightweight. High efficiency and less heat dissipation. Protected against short circuit, over current and over voltage (through PWM controller). SEC-1223 has forced air cooling and over temperature shut down. Dimensions: WxDxH 185 x 208 x 61 mm 7.28 x 8.19 x 2.40 in Shipping Weight: 5 Pounds SEC-1223 Samlex America is a switched mode power supply which converts 120 VAC, 60 HZ to regulated 13.8 VDC based on pulse width modulation (PWM) control. This unit should NOT BE DIRECTLY CONNECTED TO A BATTERY for charging or for battery back-up. Battery charging and battery back-up may be undertaken only when the battery is connected through suitable external isolating diodes and charge limiting resistor.