Cdfmxtech From United States of America, joined Jul 2000, 1338 posts, RR: 28 Reply 3, posted (11 years 3 months 2 weeks 1 day 18 hours ago) and read 2746 times:
He is talking about the 2 white squares mounted vertical to one another. They are located between the Stby Att Ind and the Cancel/Recall Switches.
Those are Auto Bright Sensors. They sense when cokcpit conditions are too bright and brighten the annunciator lights when they are in the dim position.