And it runs at 12 volts DC, not 120 AC. And, there is no battery backup, optional or otherwise.Those are sometimes called "direct wire" smoke detectors, for example the System Sensor Model 2012H Photoelectric. You can wire it up with easy to run four conductor 18 gauge wire! A big advantage is no future semi-electrician will mistake your 14 gauge smoke detector run for a good place to add a 15 amp outlet. And you can more easily branch off an existing 20 amp circuit for the detectors.
The 2012H is a smoke alarm, not just a detector. "Built-in 85dB electronic horn with temporal (3) tone NFPA72 required audible emergency evacuation signal". Check for battery backup options.