There's power in music, but not all tones are created equal. During the reign of Bell Telephone there was one tone in particular that opened up a world of possibilities: 2600 Hz. The devotees of this note were called phreakers, and in some cases they knew the telephone system better than Bell employees themselves. This episode were diving in to the early history of phreaking, how a bag of tricks was developed, and why exploring the phone grid was so much fun. Selected sources:
http://explodingthephone.com/ - Phil Lapsley's book and website of the same name
https://archive.org/details/belltelephonemag09amerrich/page/205/mode/2up - All about the Holmes Burglar Alarm system
http://explodingthephone.com/docs/dbx0947.pdf - FBI's records on Barclay and the Blue Box