Again, sorry for the bump, but the sound of this detector is not like a 769AC. The 769AC made a continuous buzzer sound like the old Firexes did. I think they used the same AC Kobishi horn. But Detector #1 that was tested in that video made a different sound. It sounded like the DC Kobishi, but heavily modulated at 60Hz. So it sounded like one of those old AC Honeywell alarms.