AT&T System 25 - Manual (Page 5)

Introduction
This guide describes the features available to you from AT&T
System 25 through a multiline telephone and provides
instructions for using the features. For your convenience, the
features are arranged in alphabetical order.
Your telephone is ready to use as soon as it is connected to the
System 25. Therefore, as you learn to use the features, you can
make and receive calls with your telephone just as you would
with any ordinary phone.
Features
Your AT&T System 25 has two types of features: fixed and
assignable. A fixed feature is one that is provided on all
multiline telephones. (In this guide, fixed features are indicated
at the beginning of the feature description by a box with a
check. )
An assignable feature is not provided automatically on all
phones. It must be “assigned” by your System Administrator.
(In this guide, assigned features are indicated at the beginning of
a feature description by an empty box. )
fixed feature
assignable feature
Check with your System Administrator as to which features have
been assigned to you. (As a reminder, you can place a check in
the box of each assignable feature as you receive it.)