I still have two analog telephone lines serving our home. We rarely use them, but having been flying on Sept 11th, I quickly realized how fast the cellular network can hit it’s maximum call connections. It’s nice to have a back-up plan!!
The main home line is call forwarded to my cell phone (a cheap hack to get Caller ID on the analog line without paying for it when it’s forwarded with the Caller’s ID). The second line was used for an older hard-wired Security service, we use it now for an occasional fax.
With all that said, It’s nice to have a visual check to make sure the analog line(s) have not developed an off-hook fault condition that we might only notice if we used the telephone lines regularly.
These off-hook units are easily connected to the older analog telephone circuits so you don’t mistakenly realize the phone line is out-of-order when you really need it during an emergency.
