[alerighi]

You can buy an ATA (Analog Telephone Adapter) to convert old analog phones to VOIP, and then use it with whatever VOIP service you want. Just be sure that the adapter supports pulse dialing since you want to use it with a rotary phone (not all does).

[wolfgang42]

If it’s being used as a “red phone” (pick it up and it immediately calls the other end), the feature that the parent wants to make sure it has is is “automatic ringdown”.