To start, let’s view the simple differences between analog and digital phone systems. Analog systems have aided organisations for generations. Built on standard copper wire and POTS (plain old telephone service) phones, are stable, have a solid voice quality, and have the standard elements you might find in at home phone such as hold, mute, redial, and speed dial. Some may even push calls between extensions. Generally that’s it. Their basic feature set and limits for expansion make them cheap to purchase. However, an analog phone structure operates on less-modular hardware so will be costly to support, configure, and enhance. For example, moving offices or extensions means rewiring a punchboard by an experienced operator. Purchasing an analog system is inexpensive in the beginning, but you’ll be tied to a closed system that requires adapters to integrate with common applications such as VoIP and customer relationship management (CRM) systems.
Digital cutting edge systems are much more advanced. Digital PBXs are designed with a robust bus structure for expanding feature sets and enabling more services. Boards are added to the cabinets for analog, digital, or IP phones. such as music, VoIP integration, and alarm systems can be enabled with modular add-on boards.
Nowadays, almost all digital systems, even if they use proprietary hardware or protocol, use an IP interface on the controller. The IP interface might allow combined messaging features such as voicemail delivery to email, fax delivery to email, voicemail transcription to SMS, click to dial, and a desktop client. These systems are considered “hybrid PBXs” because they use a mix of proprietary digital hardware and standards-based IP networking. A fully modern digital PBX is 100% IP and software-based.