Can a telephone be used to listen to conversations if only one phone is used?

A friend by complete accident picked up the phone in her bedroom and realized she could hear everything that was going on downstairs in the living room . Thinking she had left the phone off the hook down stairs she went down to replace it back in it's cradle only to find that it was already in it's cradle. She has now found that by picking up the phone in her bedroom she can hear any conversation that goes on down stairs without anyone being aware. However the draw back is her phone is very often engaged even if both phones are in their cradles. She has phoned and had the line checked and was told there is a fault with socket. We are both baffled by this and how it is possible , I would love any feed back on this , the biggest in my mind is... has this been done deliberately by someone or is it just a fluke? Does anyone have the answer . Many thanks if you have taken the time to read this .

Re-design8 years ago
THe phone downstairs is not hanging up properly. Even when it in the cradle the switch is still closed and that's why she can hear from her phone and why sometimes the phone seems engaged when they are both hung up. There is no way a faulty plug could do this. When the phone is hung up there is no power to it. Plug in a new phone downstairs and the problem will go away. Second thought - if the phones have an intercom function that might be malfunctioning and causing the problem.
colour45 (author)  Re-design8 years ago
Thankyou so much for your reply. We will do what you suggested and try a new phone . I am not sure about the intercom function I do know the phones are not the same , the one down stairs is not cordless and the one upstairs is . What you have said seems to make more sense than anything we could think of... however if this does not solve the problem I may be back to pick your brains . Thanks again .
BOOM56018 years ago
Probably a fluke.