I wasn't sure what title to list to get hits, so we will try this one first.. OK, my problem and question.
I have a simple telephone to telephone system set up to communicate with another room. I am using a 9VDC A/C adapter in series with the +9v connected to the green wire (phone 1) and the Gnd connected to the red wire (phone 2) with remaining green wire(phone 2) and red wire (phone 1) connected together.. I'm sure whoever helps understands what I am saying, if not just google "connecting 2 phones together"..
Anyways, to the question, I have a terrible hum on the line. Works great, except for the hum... I know a battery would be better, but I would rather use the A/C adapter.. I assume the hum is coming from the A/C adapter circuitry...
What do I need to do to get rid of the hum?