I have just bought a GPO 746 Rotary Retro Phone from Amazon and have it connected to a Linksys PAP-2T (Firmware 5.1.6(LS) Hardware V. 5.2.1). It's a modern phone that actually generates tones when you turn the rotary dialer, I love it and it works great for incoming and outgoing calls!
However, the phone bell ringer periodically 'tings', about once every 20 seconds, while on the hook. From my basic stopwatch tests, it seems pretty consistently every 19-20 seconds. This doesn't happen on other purely digital phones I have, I've used the ATA for some years on several DECT phones. I have 'played around' with various settings on the PAP-2T, but I'm no expert on such things, and so far nothing has stopped the pinging. I use the standard UK settings that are available on these forums and in several places around the net. Having turned off the ringer with a switch on the bottom of the phone it makes no sound while idle, so everything is fine (I can hear the DECT phone on my other extension ring), but this isn't ideal.
I was wondering if anyone had any advice on what settings to look at on the PAP-2T to see if I can stop the idle pinging. I thought it might be the SIP re-registration, but that's set to 60 seconds, and doesn't seem to correspond to the pings. I'm guess it's some sort of voltage fluctuation on the line, but changing the "FXS Port Impedance" or the "Ring Voltage" settings doesn't seem to effect it. I've asked the manufacturer the same questions, so will update if they respond. If I get no info I'll have a look inside the phone. There might be a way to adjust the ringer tolerance if there are on hook voltage fluctuations. Multimeter and brute force if nothing else!