For years, PBX systems were analog, expensive, and for big corporate players only. Small businesses had busy signals and receptionists who transferred your calls.
Small business telephone systems tended to use key systems. With key systems, each user at an extension could see and manage calls using lighted buttons on the phone. Key systems often required callers to choose a specific line to make external calls.
PBX systems for small business eventually became more accessible and affordable. Small businesses began hosting their own PBX systems.
Initially, a small business PBX system was still analog, or a PABX (Private Automatic Branch Exchange). Small business PBX systems were usually on-site, in a back room -- perhaps in an unused utility closet. Traditional PBX systems required space on-premises, and someone to manage the PBX system.
PBX systems for small business offered a lot of advantages over key systems:
- No busy signals
- Direct inward dialing (DID)
- Extension-to-extension dialing
- More internal lines and extensions available (SIP trunking)
- Fewer outside lines needed
- Lower charges for local phone service (circuit switching handled internally)
- A next-available line "pool" rather than dedicated lines for each extension, or external calls