Von Duprin does not offer a Nightlatch (NL or NLOP) function on the 8827 Exit Devices where the cylinder directly operates the exit device.
The lifting of the rods of the 8827 device is too much weight to put on the rotation of the cylinder tailpiece.
Von Duprin does offer the 373L Lever (L) function and the 377T Thumbturn (TL) function which can be setup for Nightlatch function during the installation of the Lever or Thumbturn Controls.
Von Duprin also has a K-NL and TP-NL function which requires a modified backplate on the centercase of the exit deivce to be used with the standard 880K-V or 880-TP-V trim.
In all four of these Nightlatch function options, the key cylinder rotates less than a full rotation to temporarily unlock the Lever, Thumbturn, Knob, or Thumbpiece but cannot be removed until it is returned to the locked condition (this is also known as Key Capture).
While the Key in inserted and turned (captured), the user would then depress the Thumbpiece or turn the Lever, Thumbturn, or Knob to operate the device and lift the rods.
The Key would have to be rotated back to the locked condition before the key could be removed.
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