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Old 11th Jun 2021, 1:03 am   #9
Graham G3ZVT
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Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
Default Re: "Duck" telephone

Is it environmental? I'm thinking of a nearby light dimmer or similar.
Also, as this is a new acquisition, has the seller given the mouthpiece a squirt of (electrically conductive) sanitiser that is causing the hum pickup? It's something that generated more than one service call when I used to maintain office phone systems.
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