Hi, I have an HT502 which I acquired for the purpose of getting a telephone from the 1960s connected to a VoIP service as a fun little project.
Back in the 1960s there were a number of competing ringer signaling protocols, and while 20Hz is what won out in North America, my phone uses 30Hz. As this phone has a mechanical ringer, the frequency needs to match or at least come close.
My previous SIP adapter (an OBi) supports configuring the ring frequency, but it doesn’t support pulse dialing, which is why I decided to try the HT502. I was hoping the HT502 would also support a configurable frequency, but I can’t find it anywhere in the settings.
Europe uses a frequency of 25Hz which might be close enough, so if there’s a way to configure the ringer for European phones that might work as well.