On the forward overhead there nine (blue) annunciators that have two levels of brightness.  The bright state indicates that the commanded state has not been reached yet.

I am using the FDS-SYS1 interface board from Flight Deck Solutions to connect up all the switches and annunciators of the forward overhead panel.  I could not get their recommended way for the dual brightness annunciators to work satisfactorily.  They suggest to use two outputs, one output connects to the annunciator via a diode and the other via a diode and resistor.  Since my implementation of the pressurization panel uses a Phidgets LED-64 card and I had 18 outputs left, I added some code to the panel software to drive the 9 annunciators.  The software checks for each output the brightness state and sets the output level accordingly.

The table below shows how they are connected to the Phidgets board.

For more information about the software see the panel software page.  If you have any questions or remarks please send me an e-mail at: pvrijald@planet.nl.