# Overview

You can give a mailbox certain features by assigning a Features Class of Service (FCOS) to it. An FCOS is a collection of three-digit numbers, called “feature bits;” each feature bit represents a property of a mailbox, such as the ability to log in, or the ability to keep messages. NuPoint UM includes a set of default Features Classes of Service, or you can create your own custom FCOS as required. You can assign only one FCOS to each mailbox. If you do not assign an FCOS, the default, FCOS 1, is assigned.

Each FCOS is a list of feature bits that supply different functionality. For example, feature bit 001 means the user can log in to the mailbox; 020, the user can make messages; and 050, the user can keep messages. Each feature bit represents a different, specific feature. NuPoint Voice provides more than 250 feature bits. Certain feature bits require special attention:

- Some feature bits cannot function without a “master feature bit” in an FCOS. For example, an FCOS with feature bit 021 (make and request receipt) must also include the master feature bit 020 (make messages).

- Certain combinations of feature bits are incompatible. For example, if feature bits 039 (notification tone when new message arrives) and 047 (notification prompt with new message arrives) are in the same FCOS, the server uses feature bit 047, not 039.

There are 14 default FCOS, from the basic, like FCOS 1, to the specialized, such as FCOS 4 for hotel check in. You can also create a custom FCOS by copying a default and modifying its feature bits to suit your requirements. We recommend that you maintain the original default set to aid in troubleshooting, if required.

When designing your own FCOS, see the section on Feature Bits by Category. For example, to see which feature bits allow the system administrator to create and use master distribution lists, see Category 4, Master Distribution Lists.

For a detailed description of each feature bit, see the section on Feature Bit Descriptions.

Note: Feature bits are sometimes called “FCOS bits.” This guide uses the term “feature bits” because “FCOS bits” causes confusion between the feature bit and the FCOS. Feature bits are also referred to as “features,” which can also cause confusion because many aspects of the system are also called features.