Reddit reviews Exploding the Phone: The Untold Story of the Teenagers and Outlaws who Hacked Ma Bell

So did I... Using the Red Box to get free calls and then paperclip trick when the red box didn't work anymore.

If you haven't done so already... read this book:

https://www.amazon.com/Exploding-Phone-Untold-Teenagers-Outlaws-ebook/dp/B009SAV5W0/ref=sr_1_1?ie=UTF8&qid=1485567686&sr=8-1&keywords=phreaking

It's fantastic.

Anyone remotely interested in this topic must read Exploding the Phone, by Phil Lapsley - a truly monumental effort to document this era in history.

Yes, it's as simple as that. For regular landline telephones of course. Because there's no data channel, there has to be a way for the consumer to tell(signal) the central office that the phone line needs connected to where they are trying to reach.

For years, the connections between central offices were also using a similar system to communicate between their electronic systems, ie their "switches" as they were called.

There was even a large community of people who took advantage of how the system worked to obtain free phone calls. They were called phreakers.

https://en.m.wikipedia.org/wiki/Blue_box

For a fascinating read about the early years of phreaking see

Exploding the Phone: The Untold Story of the Teenagers and Outlaws who Hacked Ma Bell https://www.amazon.com/dp/B009SAV5W0/ref=cm_sw_r_cp_apa_.uV9Bb9Y40GGD

I've met the author. A key takeaway which he leaves out is that despite changes to the telephone systems that happened in the 80s, clever methods existed that allowed these same concepts to work well into the 2000s. And this doesn't include what's possible with VoIP.