Last week I received a question via email from reader Marshall Wilgard. It seems that he is having trouble with a Grandstream BT-200 desk phone.
For five years, I used a Grandstream BT-200 IP phone without any problems. Six weeks ago, a loud hum appeared on the phone as soon as I picked up the handset. About 10 days later, the hum vanished, for no apparent reason. However, about 10 days after that, the hum came back, for no apparent reason. Despite my rebooting the phone three times, the hum remained. Then approximately 10 days after the hum returned, it vanished again, for no apparent reason. My phone has had the latest firmware for more than a year, and my VoIP provider says the problem is not with it.
Hum like Marshal describes is usually an analog phenomenon, not something that I’d associate with firmware. It sounds to me like a problem with the hardware. Issues of hum tend to revolve around a problem with the power supply. Given the age of this phone I’d guess that most likely some kind of capacitor is failing.