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.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.