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Problem: Hum

Hum is generally due to the introduction of AC power supply noise into the non-packet parts of the voice path. Typical causes are wiring running too close to power transformers or power lines, leaky power supplies (typically "wall bricks") and common mode noise due to poor grounding.


Users report a noticeable low frequency hum.


Try to correlate the incidence of noise with specific routes or pieces of equipment (including telephone handsets). Possible causes include the power supply to the handset, if an IP phone, or the routing of loop wiring if an analog handset.

If the problem appears to be associated with a specific route that connects to an analog or TDM trunk then check the Gateway for possible problems.

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