Also known as analog lines, POTS is the traditional method to support making and receiving phone calls over the Public Switched Telephone network. With the many benefits of data network services, there aren't many cases where POTS lines are the best way to go. Usually they are only need when a device needs a loop start. Gradually, the ILECs are phasing out POTS service and in many areas of the country, you can't even order it, anymore. For instance, Hurricane Sandy wiped out most of the copper infrastructure in New York/New Jersey and Verizon did not repair. They replaced it with fiber and wireless infrastructure.
Businesses, however, may prefer the security of a local system. They have the option of purchasing a private branch exchange (PBX) server to handle all their calls from local hardware.

Voicemail systems can be as simple as an answering machine or as complex as a system processing messages for an entire building full of people. Any type of business needs more than just a single mailbox answered on a single desk – even a business of one needs to keep personal and professional calls separate. The larger a business gets, the more robust its voicemail systems need to be. With VirtualPBX small businesses benefit as much as large enterprises when it comes to professional, customizable voicemail systems.
Common, but optional, equipment also includes headsets, speakers, analog phones, microphones, and even professionally installed conference rooms with things like digital whiteboard screens.