Asterisk next generation telephony

PBX ?????
Huh. I studied it when i am at my seventh semester computer networks as private branch eXchange. I thought it handle calls inside an organization.

Does it mean call routing inside a organization ?? Not only

Its handle the connectivity of the external PSTN line to the phone lines, modem, fax etc inside the organization.

So the organization need a extension ??
simple we can attain it since we have a PBX.

PBX hardware ??

Yeah its hardware, but why don't it be a software ?? Its just handle call routing and interfacing the organization communication with PSTN.

Yeah they, The digium is behind the Open source Software PBX. THE ASTERISK

Digium Open source telephony goes mainstream