When operating electric door openers with alternating current, the typical humming noise is audible. This noise is undesirable when electric door openers (eE, 100% ED models) are permanently unlocked, i.e. are permanently energized. If the bridge rectifier is connected between the door opener and the alternating current supply, no humming noise is generated. The door opener operates silently while the power is applied. Of course, the bridge rectifier can also be used for standard door openers if the humming noise is undesirable during short-term operation. Note: Also suitable for effeff security locks of the 809/819 model series and holding magnets.