A PBX or Private Branch Exchange, is a business phone system that doesn't need the ability to have Line Presence on all its business phones or extensions.
What is the difference between a Key Telephone System & a PBX Phone System? With the introduction of VOIP or IP Phone Systems, this old-technology question is becoming all the more relevant in your final decision to purchase the right phone system today.
I have cut and pasted the following text from a Google search, just to show you a classic example of a technically correct explanation for this question that would not only be technical jargon to you, but also throw up a bunch of new questions.
A key system has telephones with multiple buttons that permit the user to directly select the telephone company's central office phone lines. A key telephone system (KTS) is not a switch.
A private branch exchange (PBX) allows several trunks (outside lines) from the central office to be shared and the switching for selecting these lines is within the PBX. A PBX is sometimes referred to as a phone switch.
Key systems are usually found in small companies where few features are required. A PBX is usually found in larger companies that need more capabilities.
Was I right
Now your questions would be:
What is a switch? What is central office- I didn't quite understand why PBX is a phone switch and the KTS is not a switch
Why do I care- I want to know what each can do and cannot do for me
Now what do I need to have in a phone system and what not? How do I know
I am a small business, so do I have to look out for a Key Telephone System
Is the PBX Phone system not for me
Is the PBX more expensive
Well I don't want to be stuck with something that is having few features, so what do I do
What other features does a PBX have, which a Key Telephone System doesn't have.....But I know somebody who has a business phone system and he says its a PBX... he has a staff of six! And I am confused! Did he get cheatedor Did he pay too much for something he didn't need
Gosh, I didn't even know there were two different types of phone systems
Ok. Here is my version of the explanation...
And this is really the most important thing you will ever need to know in today's market, where there are hundreds of new phone systems with VOIP technology, IP PBX Systems, IP Phone Systems that are competing with the Panasonic, Nortel, Avaya, NEC, Samsung types.
Just recently during a sales meeting, a prospecting client was all in favor of the new IP PBX from Microsoft...the Microsoft Response Point, but it was this KEY difference, (no pun intended!!) that made them reject the Microsoft Response Point and choose the Traditional PBX from Panasonic.
What was this "key "difference
Key System Functionality is seen when each business phone or extension connected to your business phone system is able to have a button ( called Line or CO Button) dedicated for each Phone Line that you have for calling out i.e. the local telephone company or CO lines.
When you press this Line Button on your phone, you are actually connected to one of the CO Lines from your phone company.
Lets say you have subscribed for 4 business telephone lines from your local phone company then you will have Line 1, Line 2, Line 3 and Line 4 Buttons on your business phone.
You are able to pick and choose what ever line you want to dial out. Also if one of the lines is faulty you will actually hear a crackling or if it is dead then you will hear nothing except a slight hiss. In short you are able to SEE all your lines coming into the office.
You are also able to see the status when someone in the office is using any of the CO Lines, because the corresponding Line Button will be lit up RED or have a Black Triangle against it ( this feature is available in all business phone systems with slight variations.) If you press this Lit up Line Button, it will beep at you and if you have a display , it will show you the current status as LINE BUSY.
Based on my experience in the practical world, KEY Telephone Systems HAVE All and more features than PBX phone systems.
In fact this very feature of Having Line Buttons or Line Presence is a HUGE HUGE factor for most small businesses who usually have about 3 to 8 CO Lines and about 3 to 25 phones.
And what is a PBX Telephone System
In fact, the PBX Telephone System, in the practical sense, does not have the Line Presence feature or CO Line Button feature at all!
Which makes the PBX System a bit inferior when compared to a Key Telephone System. Doesn't it? Well, take my word..this is true. Key Telephone Systems today have all the features you will possibly need, whether you are a big business or a small business.
It is true, though, that if you are a very very large business , like Microsoft, or GE or AT&T etc. i.e if you need lots and lots of CO Lines than the number of buttons on your business phone, then you would go for a pure PBX Telephone System.
(That doesn't mean you cannot use a Key Telephone System for large organizations...Key Telephone Systems can be SETUP as PBX systems, but PBX systems CANNOT be setup as Key Telephone Systems. )
Didn't mean to confuse you...but ignore this comment and read on.
A PBX or Private Branch Exchange, is a business phone system that doesn't need the ability to have Line Presence on all its business phones or extensions. Now there are technical differences in how they work, as a switch, etc etc. but when it comes to your understanding,that is the KEY feature.
Both phone systems have the ability to handle multiple lines, multiple conversations, auto-attendant, voice mail boxes, for a wide range of office sizes.
The really really important thing to know today that most of the IP PBX Systems or IP Phone Systems or VOIP Phone Systems DO NOT have the Line Presence feature.
And if you think that's important to you, just like my last client did, then please don't opt for the IP PBX Systems. You will have nothing but a nice headache!
But you will want the latest and the greatest or the simplest and easiest IP PBX systems or VOIP PBX Systems, if you like the other features it has.