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What’s the difference between a Key System and a PBX?

Key System vs PBX

Key System & PBX

A telephone system is a critical piece of infrastructure for any modern organization. It connects your business to the outside world and enables employees to communicate effectively with each other and with external clients and partners.

A Key System and Private Branch Exchange (including traditional PBXs and IP PBXs) are the two major phone systems used in today’s market. The best solution for your business will depend on the size of your organization, how many handsets you need, how many calls you handle, and what type of features you want to use (voicemail, conference calls, advanced call queuing etc.).

Key System or KSU (Key Service Unit)

A Key System is a basic multi-line business telephone system, typically used by smaller organizations with fewer than 50 employees. Key System handsets have multiple buttons representing individual lines. Users pick up the receiver and press a button to access a line, and the button lights up to show the line is in use. Key Systems offer limited features such as hold buttons, speakerphone, intercom, and paging.

The fundamental difference between a Key Systems and PBX’s is that a key system doesn’t actually switch calls. It simply selects a PSTN line for the call to use, and the switching occurs at the Central Office (PSTN Exchange). The main advantage of a Key System is price, with Key Systems being much less expensive than PBXs.

Private Branch Exchange & Private Automatic Branch Exchange

A Private Branch Exchange is a business telephone system that switches calls internally between users and also allows users to share a pool of external lines or trunks for local, long distance, and international calls.

A PABX is essentially a miniature version of a public telephone exchange, offering support for multiple handsets, modems, fax machines, conferencing systems, and many other communications devices.

PBXs are much more sophisticated, flexible, and scalable than Key Systems, with more advanced features, but at a higher cost. PBX systems may be on-premise or hosted and can support thousands of trunks and extensions.

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