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.

The five cost buckets of a business phone system

A single figure on a quotation tells you almost nothing, because two quotations can contain completely different scope and still look comparable. Breaking the total into five categories is what turns the comparison into something you can actually reason about.

Two proposals that look similar on the first line of the quote can diverge sharply once these are separated. That divergence is where the budget surprises live.

Why total cost of ownership beats purchase price

The number on the quotation describes a purchase. The number that describes your actual position describes an ownership period, and the two are rarely close together.

• Equipment reaches the end of its serviceable life on a schedule that has nothing to do with whether the platform still does what you need.
• Licence and support terms get renegotiated at renewal, and the price can move considerably from where it started.
• Each successive migration is less painful than the last, but it is never free and it never stops.
• Undocumented manual changes accumulate across a large estate until nobody is confident what the configuration actually is.

This is not a claim that one model is cheaper. It is a claim that a comparison made over a procurement cycle will systematically understate the cost of whichever option has less near-term expense.

Related reading on the Newrock site

• OM50G IP-PBX for growing organizations
• OM200G IP-PBX for larger sites
• How to Choose an IP-PBX: 8 Questions to Ask
• What an IP-PBX Actually Costs