While it is perfectly acceptable to have a shared line that is assigned to both a voip phone and an analog device, there is no guarantee things won’t get wonky.*  Let me demonstrate with a recent example I came across.

Users were reporting that occasionally when calling an extension they would get fast busy.  A quick look up in CUCM showed that the directory number was assigned to several phones and two ATAs. Cue huge sigh.  For those not familiar, ATAs all provide the excruciating pains of troubleshooting analog, in a tiny, fits-in-a-bread-box, device.

Immediately suspecting one of the ATAs, each connected to a classic 5.8 GHz cordless analog phone, I did a quick check to be sure the tiny boxes of evil darkness (TBEDs?) were registered. After confirming ports on both ATA devices were up basic settings in check, I decided my time would be best served with some log…