Examine the power supply or transformer to verify that the output voltage is at the listed rating.  Verify that the power source can handle the current draw of all electrical components in line with the power source.  Verify that the power wires leading to the electric strike are of a large enough gauges to handle the current requirements.  Note: drop is higher on smaller gauge.  Using a multimeter, verify that the input voltage is within the recommended limits (+-10%).  Confirm that the input voltage at the installation stie is DC or properly rectified AC.  Verify that all peripheral devices such as bridge rectifiers, SMART-Pac III, buzzers, LEDs, etc. are properly connected.  Check that the switch, key pad, etc., meet the voltage requirements for the system.