VOIP PROBLEMS Poor voice quality, Ground

Symptoms- Voice in one direction sounds like its “your talking in a barrel”. DTMF tones are not being passed. (Laymen’s terms when calling an auto attendant you can’t dial an extension). Voice quality severely deteriorated.

Cause- Telecom equipment, Cisco or VOIP equipment Not grounded, Ground drain connected on T-1 interface cable on both sides.

Fix- Isolate Ground on one end going into VOIP Equipment that has the CODEC’s. RJ-48 pins 3 6 Ground return, DB 15 pins 2 & 4 Shield ground drain. Ground Cisco router or other VOIP equipment to Ground following the procedures of the manufacturer. Make sure that NIU and all Telecom Equipment is also Grounded externally.

The lessons of the Legacy D-4/ TDM Network devices are being ignored and it is causing massive issues. Early on in the deployment of TDM’s and D-4 Channel Banks. The manufacturers and field representatives faced these same issues that are infecting the VOIP deployments now.
The Root Cause analysis is that analog to digital conversion uses ground as its reference . Yet along the same circuitry and circuit paths the same ground is being used to drain excess energy. The voltage that is put on the ground circuits and then follows least path resistance to ground. Which without external paths is back through the circuitry to the point of “reference ground”. (Minor difference of energy on a ground create a ground loop causing further issues.)
You might be thinking wait this is VOIP, that is true but there is still an analog network out there. Where the VOIP equipment attaches to a PRI or DS-1 (T-1). At some point you go from VOIP to Analog to D-4 (Digital) and this is where the problem occurs.
When a CODEC is looking at at analog wave form and converting that into a digital output signal . Any energy on its reference (Ground) is translated into either a higher or lower level. If you are reading 1600 HZ and converting that to 00100111. The First step is to determine what is 1600 HZ. With Ground as reference 0 then you can make the conversion easy. But if you add +.002 V or -.03 V to the ground that interferes with the ability to accurately convert the signal.
The fix then is to isolate the grounds in the circuit that are reference from those that are drain. On a T-1 interface the pins are 3 & 6 on an RJ-48 that is used to drain excess energy from the cable. If it is attached at both ends then the excess energy is following the path back into the router and into the reference. Remove the pins or these wires from the router side and leave them attached on the NIU. The NIU should have an external ground that is attached to the building and excess energy will follow this path. Further Follow the manufactures procedures and attach a ground between the router and building reference. This will provide a path for excess energy out of that equipment.
(just a minor note use smaller wires towards the equipment then towards the building. IE if the building common ground point is using 6 awg then use 10-12awg to ground the equipment.