Can vintage rotary telephones be used with VoIP?

I'm not sure if what you want can be done with no modifications, but it can be done. I can think of two things to consider. The first is analog rotary dialing. Most VoIP ATAs do not support this. However, I have read reports that the Grandstream HT-502 does. See this forum thread: http://www.dslreports.com/forum/r21626866- If you don't have an HT-502 or don't want to buy one, you can also get a device that "translates" pulse dialing into DTMF tones. Here is a list of such devices: http://www.voip-info.org/wiki/view/Dial+Pulse+to+Touchtone+DTMF+Converters Here is a less expensive device, but I have not tested this one: http://alldav.com/index.php?main_page=product_info&products_id=30 The other thing I can think of to consider is REN (Ringer Equivalence Number). Phones with mechanical bells use a lot of power to ring. Comparatively, cordless phones do not since they plug in to AC power. Your vintage phone probably has a REN of 1.0 - this may be printed on the bottom of the phone if you want to see if I'm right. The HT-502 supports 3 REN. This means you could use three mechanical bell phones. The Linksys PAP2T and SPA-2102 also supports a maximum load of 3 REN, the OBi100 supports 5 REN. Good luck with your project!

If you have VoIP hardware that has modular jacks for plugging in phones, then I guess you could get an adapter that would convert an old-style 4-prong phone plug (like a rotary phone would have) into a modular connector - that way you could plug the phone into the VoIP hardware. That might work for incoming calls and ringing, but it wouldn't work for dialing, because rotary phones use pulse dial, but I'm pretty sure VoIP hardware only works with tone dial. Maybe you could connect a newer phone to do the dialing out.