TLDR spoiler: Does a device exist which acquires an internet signal from WiFi (ideally) or ethernet (tolerable) and into which one plugs a conventional landline telephone in order to utilize Optimum’s internet-based telephone service?
[/TLDR summary]
Until last week, we had two separate Optimum accounts, therefore two separate cable internet modems: one for internet downstairs and one for internet upstairs. We also have Optimum for cable television and for the landline phone, the latter two being associated with the downstairs account.
Last week we decided we didn’t need two separate internet connections — the wireless signal from upstairs is sufficient for downstairs. The upstairs modem is a separately purchased Arris modem, not the one that Optimum rents out to you by default. This is in order to have complete control over ports and which ones get forwarded and which ones blocked and so on.
Optimum was informed of this and given the serial# from the downstairs modem; they said they’d interrupt the signal and we should bring the device into the shop for credit.
All the wired and cords were unplugged from the downstairs modem and we were preparing to take it in when it came to our attention that the landline phones no longer worked. TV service is fine, just the phones. Called Optimum tech support and they verified that yeah, the phone depends on the cable modem. It could get its internet signal from the upstairs cable modem instead, except for the small problem that unlike the standard Optimum-supplied cable modem, this Arris modem doesn’t have a port into which to plug a telephone line.
So (finally), QUESTION: Can I purchase a device that we set up downstairs which connects to the WiFi signal and into which I can plug this phone line, so as to cause the phones to work the way they do when plugged directly into the back of Optimum’s cable modems? Or one to which I run a long ethernet cable? Or is there any other logical way to connect the landline phones short of continuing to pay for a second cable modem and IP address that we only need for the damn phones?