Information Systems:Phone System Troubleshooting Checklist

Use this page as a starting point for diagnosing and troubleshooting issues related to the phone system. Issues and fixes should be added here as they are encountered, for future reference.

Troubleshooting tips

Problem	Suggested fix
Need 3CX configuration support	3CX has excellent documentation on its website, as well as a very active forum. For critical issues, RingOffice offers premium support. 3CX also offers premium support at $75 per ticket/issue.
Modify existing VoIP services	Use the ThinkTel and RingOffice web portals.
No dial tone	A dial tone indicates communication between the IP phone and 3CX (not necessarily related to SIP trunks). If there is no dial tone, the phone might not be connecting to the PBX. Check physical network connections as well as extension registration (via the phone's menu or web GUI).
3CX not accessible after firewall changes i.e. phone system seems to be down	Reboot the firewall. Caution: Rebooting the firewall reboots the firewall. Know what you're doing first.
Outside caller cannot reach an internal extension directly	Use uControl to check that the number is assigned to the main SIP trunk and not the reservation trunk. Check 3CX to see if an inbound route exists.
Headset not working	Try unplugging the headset and plugging it back in. Also try restarting the phone from the 3CX web console.
Call history inaccuracies	check to see what 3cx webclient thinks should be the Primary Phone

Notable issues

Issues past and present worth documenting for reference.

One-way audio during calls

A few weeks after going live with the new phone system and service, users reported random one-way audio drop-outs i.e. mid-call one party would suddenly be unable to hear the other.

The culprit was UDP Flood Protection, which is a firewall mechanism that protects against a flood of packets by temporarily blocking the IP if the packet rate (pps) exceeded a certain level (configurable in the web GUI). The fact that there is lower visibility into this mechanism (i.e. events log to a separate file for a module which is otherwise deactivated (Intrustion Prevention) besides these flood protection mechanisms) is a known Sophos quirk (check the community forums). The randomness would be due to a sudden block either in the transmit or receive directions of RTP audio. An exception was added to forgo UDP FP for traffic from/to the PBX.

Headset automatically picking up calls

EPOS headsets have call control functionality that allow incoming calls to be picked up using the Call Answer button on the headset. The normal behavior is for the Call Answer signal to be sent only when either the button is pressed, or the headset is taken off-hook i.e. removed from the base (on-hook). However, Customer Service agents reported that calls were at times and randomly being automatically answered (picked up) without a button-press and while off-hook (e.g. call answered while headset sitting on desk or being worn while walking down the hall).

Update May 2021: This issue has been resolved. The headset is functioning correctly and the undesired behavior was due to a) two headset features that were enabled and working as intended but not desired and b) a misunderstanding of how link establishment works with these Sennheiser headsets. Specifically, the headset can be in two states (when not docked on the base) - Link established, or not (link off). For simplicity sake, the Link established state is analogous to a mic being hot. This is indicated by a lit blue LED on the base (and on the headset). In this state, any audio will play on the headset and receive audio on the mic. However, with the 3CX softphone, there is no simulated dialtone as there is with the deskphone, so there is only a visual cue (unless you have excellent hearing and can hear the white noise) that the headset is in this state. Moreover, in this state, calls are auto-answered, as this is analogous to having the button pressed on a PA or intercom.

The way the Link established state can be unknowingly/accidentally activated is where the two features come in. Namely, Auto Link and USB Auto Audio establishes a link in response to taking the headset off the base and activity detected on the USB port, respectively. Neither of these are desired features in our environment. Also, pressing the headset button a second time after ending a call (since there's a delay in the response) can leave the headset in this state unknowingly. This explains the random and inconsistent nature of the auto-answer behavior. Consider a scenario where user habits cause them to press the button multiple times after call end (thinking the button press didn't go through) - then the headset is more likely to be in this state throughout the day. Consider another scenario where the headset is set as the primary audio device, the headset is offhook, and notification sounds come through - then USB Auto Audio will establish a link to the headset so that the notification sound is pushed through, and a subsequent call will be auto-answered.

TL;DR, disable Auto Link and USB Auto Audio, and train users to be mindful of the Link established state (blue LED). These features are best changed in EPOS Connect, which overrides the rocker switches on some models (e.g. D10).