If the cable provider offers digital voice, they're required to have backup power for their infrastructure for at least 24 hours (or 8 hours under older regs) t

If the cable provider offers digital voice, they're required to have backup power for their infrastructure for at least 24 hours (or 8 hours under older regs) to allow for 911 calls. The power injectors used for cable amplifiers usually just have a couple of lead-acid batteries in them.