POTS Replacement

There are wireless home phones that claim to support fax and there's digital service with the same claim. As far as alarms go, you'll need to check with your alarm company to see what they will accept. I have a wireless home phone, from another carrier, that claims to support fax, in my experience if you set the fax speed as low as it will go and turn off error correction they will work, but not reliably every time. Fax and the older alarm equipment were analog and not really intended for other types of signals, they didn't even have other types of signals when they were first developed. I think most alarm companies have come to accept the digital world, but it may take an upgrade in equipment. 

Two main options, VOIP using internet service or cellular from tower…. Over the years security alarms have been going cellular to avoid hardwired interruptions from cut or damaged lines using telephone, coax or fiber… if hardwired then may need cellular backup which is becoming more used for businesses.

Verizon has stated that 1/3 of their FWA (fixed wireless access 5G internet) is sold to businesses as backup service to customers fiber connections.