A:  I believe these were the 1st Generation. I can’t find where it lists it in the manual, so I’d have to assume 1st Gen. Hoping the link below from the units helps.  https://images.thdstatic.com/catalog/pdfImages/d6/d66ea265-817e-486a-aabe-d316a5347f32.pdf

A:  Hi there, Gigi. There are multiple ways to identify what generation of Nest Protect you have. We recommend checking the link below to help you with quickly identifying the type of Nest Protect you have: https://support.google.com/googlenest/answer/9232605

A:  You can operate it without a cellphone and app, but you need the cellphone and app to do the initial setup.

A:  Hi, oscar! Nest Protect requires the Nest app for the set up process. The app has complete detailed instructions and will guide you through Protect setup and installation. Once it's set, it will continue to detect smoke and carbon monoxide even without the app. If you want to maximize the Nest Protect's features and receive notifications, we highly recommend using the app. Take a look at this link for the complete setup requirements and guide on how to setup/install: https://support.google.com/googlenest/answer/9247146

A:  Hi, Jimbo! Absolutely, Nest Protect (Wired 120V or 230V) and Nest Protect (Battery) are compatible and can interconnect with each other. They can communicate if they're within 50 ft (15 m) of each other inside a home. Take a look at this link for more info: https://support.google.com/googlenest/answer/9232615

A:  Yes, I have a mix of both wired and battery nest's and they all work together with no issues.

A:  Hi there, Robert. Wireless Interconnect is the way that your Nest Protect in the hallway tells all of your other Nest Protects when there’s a problem. Both Nest Protect (Wired 120V) and Nest Protect (Battery) use Wireless Interconnect. It also lets you add more alarms without adding expensive wiring and it allows your Nest Protect to convey more safety information in an emergency. Each company’s smoke and CO alarms use proprietary detection algorithms and interfaces. We recommend reaching out to the manufacturer of your non-Nest smoke detector so they can provide you more details about your concern. If you need further assistance with the Nest Protect, please don't hesitate to contact us on our Google Help page here: https://support.google.com/googlenest/gethelp