At this point I'm willing to say this is a Telo problem . It works fine for a while (could be weeks), then a call comes in and after it ends, by either hanging up or leaving a VM on the home system, the analog side of the Telo stops functioning. The flower shows "blue" as in normal operations, the Telo network interface responds to ICMP ping, and the Telo shows as "online" on the Ooma web site. I can even use the Telo to listen to a VM that was left. Outgoing calls from the house just fail. Incoming calls go to Ooma VM. Coincidently, whatever is happening to the analog phone line is also leaving my ADT alarm panel in a state where it's trying to communicate via its download protocol too. While that may be of diagnostic value, it isn't causative, and rebooting the Telo puts the ADT system back into normal operation.
Nothing else to do but wait for Ooma to fix this. At least my ADT system, monitoring the phone line, sees the failure so I'm notified of it immediately via it's cell connection (which leaves VM with Ooma that alerts me the failure has happened), and I can then power cycle the Telo to restore it before anyone else in the house finds out and criticizes my choice to move to Ooma.
Here are dates of failures since last post. Fix is to power cycle the Telo.
Jun 5, 12, 25
Jul 16, 18.
Oct 26, 28
Nov 12, 13, 23, 28
Dec 9 (2019)
Hmmmm. Made a call today to an automated voice system. I was about 3 minutes in and the call just dropped. Got a kind of pulsing sound, like someone picking up another extension and hanging up at about a 2Hz frequency. Of course no one was. Telo was left in same state as described in the earlier problem description and needed to be power cycled. The difference this time is that it happened a ways into an outgoing call, not shortly after an incoming call. Don't know if that means it's the same problem or not. This is my first experience with this on an outgoing call ...?
I've also purchased a "loop current" measuring device. Under normal operation, the loop current put out by the Telo with a single phone attached to its phone jack shows up as low (< 22mA). "Good" loop current is between 23-27mA. A loop current booster did not fix the problem and per its manufacturer this would be the case if the Telo actively regulates the current to be too low.
I have located on the web this list of problems that a low loop current can cause for analog phone systems in general. Symptoms of Low Loop Current Problems are:
poor voice transmission quality low volume
lost calls during transfer
I haven't experienced any of those problems, but its disappointing to learn this is the case for the Telo.