Brief Introduction about Asterisk

How to install Asterisk PBX:
https://www.amazon.com/Complete-Asterisk-Training-install-configure/dp/1796396974/ref=sr_1_1_sspa?keywords=how+to+install+asterisk&qid=1583443998&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFKTlREVU1TMDRDSzYmZW5jcnlwdGVkSWQ9QTA3MjY1NjUzTFBMVERITDlBNVgmZW5jcnlwdGVkQWRJZD1BMDY3MjA1MTNKNk80NDhQNTYzQUEmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl