Those two potentiometers are for voltage and current control? Yes , see photo . What means that letter "P." ? Is that tumbler main ON/OFF switch? Yes , when switch is ON , P. lights . Those green numbers show voltage value? Yes . What circuit have you used for those LED numbers? http://www.ebay.com/itm/DC-0-99V-Mini-Digital-Voltmeter-Blue-3-Wire-0-36-LED-Display-Panel-Volt-Meter-/160914959288?pt=LH_DefaultDomain_0&hash=item2577476bb8