An excellent source of technical information and hundreds of links! Very informative.
Private Line Magazine's Home Page
Phone Trips - Phone Phreaks of the 1970's - Many interesting audio recordings of various dial tones, busy signals, stepper switch sounds, etc.
|A Tour of the Pacific
Bell Central Office
at 611 Folsom Street- Section 1
Sound Recording Research at Bell Labs
Roseville/Stepper.htm The sounds of Roseville Telephone Museum's step by step switch