Dr. Firestone and Dr. Grey messages on the Simplex voice evacuation system

I was watching this video on all the tones and messages of the Simplex voice evacuation systems ([All Simplex messages and tones from firealarmcollector.com - YouTube]), there were two messages that really stood out and I don’t know what they mean.

1st message: “Dr. Firestone, please dial 2829.”
2nd message: “Dr. Grey, please dial 2353.”

(I just realized I put this thread in the wrong topic. If anyone knows how to move topics, please let me know.)

Not sure what “Dr. Grey” indicates (though it’s probably referring to a hospital code with that color), but “Dr. Firestone” is another way of saying “Code Red”, which is the hospital code word for fire.