Why was I sometimes able to hear my neighbor’s phone calls on my phone back in the day

Question

I was a teenager in the 90s, so I was on the phone constantly. Sometimes I could hear someone else’s phone call on my phone while I was talking to someone.
Sometimes they could hear it too, sometimes not. And I do recall this happening to my friends sometimes as well.
And how often could someone else hear my conversation?

In: Engineering

Answer 1

Also around that time, cordless phones were not encrypted.

I had a police scanner and I would pickup phone calls and baby monitors nearby my old apartment.