Wow!! I have no idea how you find all this information Mr. L! Every time I search for “Probe smoke detector”, I only get hundreds of results for duct detector air sampling probes. Thank you so much. You are the man!!
Okay, now I know what Probe smoke alarms look like. They resemble Firexes. Come to think of it, I think there was a Probe smoke alarm in my sister’s old house from 10 years ago. I just thought it was a Firex, or a “Maple Chase”. It’s cover disappeared soon after it voiced it’s opinion of my sister’s cooking. I wish I kept the detector. It eventually was replaced and scrapped.
I believe Probe alarms have similar side vent-slots to the 76RC’s cover, but instead of being evenly spaced, they are paired up in twos.
Also… I found a news story from 1981, about the different kinds of smoke alarms. They test a board of 5 alarms, which I have closely examined and deduced what their test number and type are.
There are other alarms featured, however, the video is so washed out you can’t see the cover designs. (Like at 2:06).
Here’s a still showing the board. The detectors are numbered from bottom to top.
Detector #1 is a 120VAC (probably hardwired) ion alarm with a squealer. It might be a GE. It makes a sound like it’s running on FWR power. It makes the high DC squealer tone, but is heavily modulated at 60Hz.
Detector #2 could be an ESL. It is a 120VAC wall cord Photo alarm. It has a squealer, but it makes the sound of a full DC squealer.
Detector #3 is COOL. It is a battery powered Ion alarm. This is the one I thought was a “Probe”. It looks like a First Alert 76RC/RS, but has a piezo horn, and the test button is not in the rings, but in the little circle near the center of the cover!
Detector #4 is the 2nd Gen rectangular GE alarm. Not much to say on this one. It’s more common.
Detector #5 is a battery powered photo ADT alarm, with the same black Star buzzer in the old GE alarms.