Rather than flashing every time a station presses their CALL button, this light only comes on when a CALL button has been pressed four times quickly. It starts out solid, then after a while starts blinking.
Perfect for getting a specific person's attention and ONLY when you need that specific person. I use this for the conductor in the orchestra pit. They just can't see the little call light on their intercom station.
This project uses a couple of modules and minimal soldering.