Inside Macintosh: Telephony /

Chapter 4 - Call Appearances

About Call Appearances

A directory number can be associated with a call appearance (or, more briefly, a call). A call appearance is a connection between two or more directory numbers, for instance, when one telephone user places a call to another. Directory numbers can carry several call appearances concurrently (for instance, when a telephone has a Call Waiting feature or a Conference feature).

At any particular time, each call appearance is in one particular state. For example, a call appearance might be in an alerting state (ringing or flashing), a held state (on hold), or an active state (meaning voice or data can flow end to end). The Telephone Manager provides a large number of functions that you can use to initiate, answer, or otherwise manipulate call appearances.

A call appearance can have some or all of a large number of capabilities or features. In fact, there are so many features that can be applied to a call appearance that the Telephone Manager uses two bit fields in a call appearance structure to store information about the features of a call appearance (the featureFlags and otherFeatures fields). See "Call Appearance Feature Flags" on page 4-15 and "Other Call Appearance Feature Flags" on page 4-17 for a compete description of the available call appearance features.