Do I need an external power supply for the door strike? Can I get the power off the board?

For the TX3 series 2 door card access panels you have 2 powered/wet outputs #7 and #8 that supplies a 12Vdc (solid-state) 1 amp-shared for door strikes and maglocks or 700mA if you are using only 1 output out of the 2, within fire code requirements.