Once upon a time in 1936 rotary dial telephones were introduced by the Bell System. This introduced telephone subscribers to “dial tone” which indicated the phone system was ready, the “ringing signal” which indicated the phone number you just dial was getting the phone call, and the “busy signal” which indicated that the phone number you just called was already on the line with another call. Here’s a video that explains the whole process.
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About the Author:
I am a cybersecurity and IT instructor, cybersecurity analyst, pen-tester, trainer, and speaker. I am an owner of the WyzCo Group Inc. In addition to consulting on security products and services, I also conduct security audits, compliance audits, vulnerability assessments and penetration tests. I also teach Cybersecurity Awareness Training classes. I work as an information technology and cybersecurity instructor for several training and certification organizations. I have worked in corporate, military, government, and workforce development training environments I am a frequent speaker at professional conferences such as the Minnesota Bloggers Conference, Secure360 Security Conference in 2016, 2017, 2018, 2019, the (ISC)2 World Congress 2016, and the ISSA International Conference 2017, and many local community organizations, including Chambers of Commerce, SCORE, and several school districts. I have been blogging on cybersecurity since 2006 at http://wyzguyscybersecurity.com