The difference between 1477 and 1400 Hz is 5.5 percent. It's possible your alarm panel can detect a tone within that bandwidth. (Even with the 697 Hz tone playing at the same time.) It's the kind of thing where you have to experiment.
Or, you might obtain a whistle (pitch pipe, etc.) that produces 1400 Hz. That's 'F' two octaves above middle C.
Or, if you can remember how a 1400 Hz pitch sounds, and you whistle it, the alarm panel ought to detect that. Try gliding your whistle up and down around the pitch, and it could hit the right tone.