The barrel power distributor takes power input from a plug pack transformer and allows distributing the power to up to 6 ESP sensors.
The USB power distributor takes power from a USB power supply and allows distributing the power to up to 3 ESP sensors.
The power source needs to be able to provide a minimum of 1W to each sensor. For the barrel distributor, a minimum power supply of 12V/500mA should be used to power all 6 ports. For the USB distributor, only 2 sensors should be run off a standard computer USB port and a higher-power supply used to power all 3 sensors.