There are a variety of different types of phone systems available to businesses. Each type provides a different mix of features and functionality, and may be incompatible with other types. To ensure your office phones work properly and efficiently, it is important to select the type of phone system that is best suited for your company.
The following are the 3 common types of business phone systems.
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1. PBX On-Premise Systems
A PBX (Private Branch Exchange) is used by large organizations to provide local telephone service in an office environment. The PBX is configured to allow calls within the organization, but may also provide for connections with outside lines through trunk lines.
Tie trunks permit any external line to be routed to any of the internal telephone extensions. Some are proprietary systems that are unique to a single manufacturer. A PBX may use an integrated system design approach, or it may consist of multiple components from different vendors with varying degrees of integration.
External trunks allow direct connection between the PBX and other telephone company equipment, such as the telephone company’s CO (central office).
PBX systems are very flexible in their configuration. They can support one or multiple users. A PBX is generally configured with many standard telephones, but some PBXs also provide for special telephone sets; e.g., a speakerphone or headset that can be used in conference or training applications.
IN/OUT trunks provide connections to the telephone company switch. A PBX with only IN/OUT trunks is known as a Key Service Unit (KSU), and differs from a PBX with both IN/OUT and tie trunks, which is sometimes called an Enhanced Service Unit (ESU).
2. The VoIP PBX
The VoIP PBX is like a traditional analog PBX. It provides telephone service using Voice over Internet Protocol (VoIP) technology. An analog telephone can connect directly to the VoIP hardware device, which typically includes at least one FXS port for connecting an analog phone or fax machine.
Alternatively, a telephony device that is capable of connecting to the LAN can be used with the VoIP hardware device. In this case, all devices connect to the telephone system through a standard NIC installed on each device.
A basic analog PBX provides only internal extensions and typically connects directly to the telephone company CO (central office) or PBX. By contrast, a VoIP PBX can support an internal analog extension and many different devices; e.g., an IP telephone (softphone), SIP telephone device (hardphone), analog phone, fax machine, etc. illustrates the components of a VoIP PBX system.
A VoIP PBX can be connected to the Internet in one of two ways:
Gateway Mode
The VoIP hardware device acts as a gateway that connects multiple devices in the office, such as telephones and fax machines, with standard phone cables to the Internet. This setup requires that all devices in the office, not just the telephone system, be connected to the VoIP device using standard phone cables.
Hybrid Mode
A hybrid PBX provides direct connections between telephones and fax machines in an office environment with IP-based telephone service without requiring that these devices be directly connected to the Internet.
The VoIP hardware device is connected to the local area network (LAN), which in turn provides connections from telephones, fax machines and other LAN-based devices to the VoIP hardware through a standard Network Interface Card (NIC). A hybrid PBX can also be referred to as a soft PBX or IP phone system.
A VoIP PBX can support a variety of services, such as:
Voice Mail
Similar to the type of voice mail available with a traditional PBX.
Telephone Conferencing
The VoIP telephone system provides conference calling at reduced cost. Conference calls may be limited by the number or type of participants that can be accommodated simultaneously.
Fax Service
Fax services can be provided using a traditional fax machine or a dedicated fax server.
Analog Modem Service
Analog modems may be connected directly to the VoIP device, or they may be connected to other devices on the LAN that are then connected to the VoIP hardware. Many types of modems are available, and some VoIP hardware devices support a variety of these modem types.
Voice/Fax Mail
This service provides voice messages to the user for fax messages received at the station. The number of incoming messages is recorded on one line and then forwarded to an extension or group of extensions as a fax message.
3. VoIP Phone Device Hosted on the Internet
A hosted VoIP phone device or hosted IP PBX is a type of telephone system that provides telephone service to multiple users by using an application service provider (ASP) rather than acquiring and maintaining physical equipment.
It is similar to a traditional analog PBX, with the primary difference being that it uses the public switched telephone network (PSTN). In some cases, a hosted VoIP PBX can deliver extended features that might otherwise be available only on a private branch exchange (PBX) system.
The traditional PBX uses internal trunks, internal extensions, and analog phones as connections from the central office (CO) or PSTN. In contrast, a cloud-based solution uses a connection from the PSTN or CO to connect to one of the servers. This server acts as a gateway from the cloud-based system to outside telephone users and can provide dial tone, hold music, paging alerts for each internal extension, and other features. Each internal extension is connected to this gateway through VPN software installed on each device.
For example, a tenant in an office building might acquire a full-featured hosted IP telephone system. The tenant would then have the capability to connect telephones and fax machines, as well as PBX features such as call forwarding and conferencing. A hosted VoIP phone device is designed to provide the features of a traditional PBX system with the convenience of a hosted service.
A cloud-based solution allows users to use any device that logs into a network to access services from the telephone company’s system. This model is also known as a “hosted IP PBX”, with the hosted VoIP phone device being a type of PBX or telephone system.
