Direct power from low voltage transformer. SkyBell is designed to work with your current doorbell’s low voltage transformer. The primary power standard to the transformer can be 120/130 VAC or 220/230/240 VAC. The secondary power from the transformer to SkyBell must be 16-36 VAC 10 VA. SkyBell can work with a 12 VDC power supply but you MUST use a 10ohm/10watt resistor in series on one connection between SkyBell and your power supply. Failure to do so will damage your SkyBell and automatically void your warranty.