> PBX Features

PBX Features
PBX systems provide a plethora of features typically offered by a telephone provider,
such as call waiting, three-way calling, conference calling, voicemail, additional call
appearances, and many other routing features. Some vendors count 600 or more separate
features among their capabilities, far more than is offered by any carrier on a
central office switch as subscriber services. But often overlooked in this list are those
used for access control.The PBX is effectively the firewall to the PSTN and because
voice access has per-minute and geographic costs associated with each call, this
aspect of PBX capability should be a critical consideration for product selection,
configuration, and ongoing operations.Yet at the same time, the data security community
is rarely concerned with this characteristic because it’s not a ppure data security
issue, yet even in a VoIP system there will be PSTN connectivity; why gamble
with this?
Say a company has 200 employees, each with a phone on their desk.
Without a PBX, each employee would require their own pair of copper wires from
the CO, each with their own phone number that routes to their desk. However, it’s a
safe bet that not all 200 employees will be on the phone all the time, and it’s likely
that most of those calls will be to other employees.This is where a PBX really pays
off. A business or campus will need many fewer lines from the Local Exchange
Carrier (LEC); in the previous example, the company might require only 40 outside
lines, routing those calls onto the PSTN trunk lines as necessary on a per call basis.
They also could rent 200 Direct Inward Dial (DID) numbers from the LEC, which
terminate though those trunk lines.The PBX will then route the inbound call based
upon which DID number was dialed to reach it.