I used to have a Linksys PAP2 ATA used with ViaTalk (Asterisk), not VoIPo. It garbled touch-tones received badly. I could call another landline and push DTMFs - they were badly clipped and distorted. As a result, most but not all IVRs (voice mails, conference bridges, bank logins, pharmacy prescription refills) failed. Not the analog phone's problem- tried many. All work OK on a POTS line. Tried changing to SIP signaling from the ATA but that didn't work because of VoIP service provider SS7 bugs.

None so far with this VoIPo ATA from Grandstream.