It’s an old FritzBox where I turned off wifi etc and just use for VOIP - Pots. When I set it up a some time ago it was EUR 15 or so on ebay, as these old FritzBoxes have no other modern use. They put out “just” enough juice to ring the phone. Ringing is softer than what I know from. my childhood, though.

Pulse dialing works, but you can’t pause while dialing as it interprets a pause as “now connect the call”. (Real POTS had “incremental” dialing)

I have these phones for fun, but if I’d need to use them I’d probably buy a new dedicated voip adapter (EUR 150+).

Old FritzBox routers are cheap here, that’s why I use them.