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The Defination of PBX And PSTN

There is a subtle, yet importance difference between PBX and PSTN.It is so hard to tell the difference between PBX and PSTN for many people.Next I will help you solve the problem.

First let’s define each:

What is PSTN?

PSTN stands for Public Switched Telephone Network and is just a fancy name for the traditional telephony we are all familiar with – where telephones are connected to dedicated networks.

As long as you know the correct telephone number, these networks allow you to call another person anywhere on the network. It’s also commonly referred to as POTS - plain old telephone system.

Getting more technical - PSTN is the collective switches and all the infrastructure (telephone lines, fiber-optic lines, and underground cables) that make up phone access across the world.

The PSTN is also further connected by Tandem Offices, and Toll Offices which increase the range of calls at a further cost. These allow for Long-Distance, and International Calls to take place.

On that point, this is also why most businesses prefer to use VoIP, so that they don’t get hit with long distance overage charges, especially for making international calls.

What is PBX?

PBX means Private Branch Exchange and is the “switch” in an organization’s premises that routes calls internally and externally to the PSTN/POTS.

In very plain terms, PBX is the software or hardware solution that manages phone calls for a building or campus.

The PBX system tells every phone on-site what their extension number is, and routes calls based on phone number, if the location has more than one.

A PBX may have other features as well - such as hosting an automated attendant, playing hold music, managing all internal calls, building groups of phones that ring simultaneously, and even queueing calls for a call center.

So, what’s the difference between PBX and PSTN?

The surprising answer is mostly in the scope. Both are switching services that move calls to their final destination. This can be done using software, or hardware solutions.

The main difference is that PSTN does what a PBX does, but over a much wider area - essentially, it finds the best route to send signals to connect a call.

The longer the distance of the call, the more bounces the PSTN needs to make to ensure the call gets to its destination. This is routed through various exchanges. These ones aren’t private, but represent different localities in much the same way that a PBX represents a building or campus.

This is why 7 digit dialing works, it doesn’t need the area code as the local exchange doesn’t need to send the call outside its purview. Like a more expansive extension number.

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