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
Back in the analogue days, you could get “Crosstalk” induced by wires being too Close together in the old telephone systems.
The old red/green/yellow/black inside wiring cable had basically no or very random twists, and no insulation making it prone to crosstalk.
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.
Imagine you have a really long plastic hollow pipe. You can talk through it and someone from the other side will be able to hear you even though you can be far enough that normal yelling wouldn’t reach. That’s what a phone line basically does.
In order to connect to multiple houses, you need multiple long pipes to each house. So you arrange the hollow pipes next to each other. But now, when you talk in one pipe, sometimes your voice reverberates into the other pipes and those listening in other pipes can also hear you.
This is called crosstalk. Where the electric field in the copper wires reacts to the wiring next to it causing the neighboring cables to also conduct the electric field. Telephone poles can hold hundreds of wires bundled together. So crosstalk was fairly common until it was cheap enough to change to twisted wiring that mitigated crosstalk. Not all wires have been upgraded though. But most have since back when dial-up was the primary form of internet for most people, you needed upgraded lines to be able to function at scale.
I’m an ex GPO telephone engineer.
Many reasons for this.
Telephone lines used to be wired in a cable known as “3 pair” which has 3 pairs or wires, usually all 3 pairs come to your house and are terminated at your main socket. You only need one pair for your telephone line to work.
It’s not uncommon, to save time by using the spare wires in your line to wire a second line ie your neighbours using the same cable. This can create cross chatter as the signal can cross to the other pair in the wire. There’s no shielding.
Another reason could be the engineer double jumpered it at the distribution point accidentally. The jumper cables used to be so brittle and snap on the breakout bar so lazy people would jumper over the top, another way of getting cross chatter
In the 70s during a gas shortage, I suddenly heard two guys on another line planning to go out that night to siphon gas from cars (this was before locking gas caps).
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