I swear whenever I see videos of people testing alarm systems the exit signs are flashing whenever the alarm goes off, and in some power outage videos the exit signs flash?
That might be to help people notice them better, which is important during either event (or at least fire alarms: during power failures that might be to save the battery).
I know my elementary school had exit signs that flashed in march time when the fire alarm went off. The panel was a simplex 4007es (originally a 4002).
I haven’t seen it at all where I live. But older Exit signs have 3 bulbs, one on the left and right for 120VAC bulbs, and a center one for a 6/12/24VDC bulb. In my area they are connected to emergency light packs to keep the signs illuminated during a power outage. I suppose one could take the DC bulb wires and connect it to the signal cct, or an auxillary relay or power supply that can flash them.
I know the exit signs at my elementary school were the ones where the led’s make up the shape of the words.