From the manual ...
*Operable with phantom power supply, minimum 24V DC regulated, however, 48V DC regulated is
recommended in order to illuminate LED.
*Utilizes standard 9V alkaline battery (not included).To install, simply remove door cover. (NOTE:
The Input activates battery.To conserve energy, unplug when not in use.) Power Consumption:
*USE DC POWER SUPPLY ONLY! Failure to do so may damage the
unit and void warranty. DC Power Supply Specifications:
-9V DC regulated or unregulated, 100mA minimum;
-2.1mm female plug, center negative (-).
Optional factory power supply is available:Tech 21 Model #DC2."