There are even further variations of these First Alert alarms. The SA76RC had both types of piezo horns (the earlier one had three holes and the later one had only one central hole). The SA120 had all the same components that the SA76RC had and it had an escape light. First Alert’s latest “old-style cover” design (as I call it) which was the SA67D, had the newer piezo horn and a newer black sensor. I own a SA67D. first Alert also came out with special Light Test alarms (I own three) around 1993. They had the same components that the SA67D had except there was a light sensor type thing in place of the LED (located under the test button).