If the power goes out, but a person has backup Internet service, would the phone lines still typically work? And if so, then does the 2400i continue working?

The CapTel 2400i/880i/840i phone requires an electrical power, phone line and Internet connection. All three must be plugged in and in working order in order for the CapTel to provide captioning support. If the electrical power is out the CapTel will not be able to power up and work.