C H A P T E R 24 Customer-Premise Switching System Features

_ Do not disturb: Users can press a button that silences the bell and
prevents intercom calls from reaching the station.
_ Forward all calls: Users can redirect all calls to another station or
destination.
_ Forward on busy or no answer: Users can redirect calls to another station
or destination if the line is busy or does not answer.
_ Held-line reminder: After a call has been left on hold for a specified
period, the telephone emits a warning tone.
_ Missed-call indicator: A list of unanswered calls is displayed
on the telephone.
_ Music on hold: While a call is on hold, music or a promotional
announcement is played.
_ Mute: A mute button on the telephone disables the microphone.
_ Paging: Stations can page over the telephone speaker.
_ Privacy: Prevents other stations from picking up a line that is in use.
In some systems privacy is automatic unless the user presses a privacy
release key.
_ Station restriction: Stations can be assigned to different classes of service
for restricting long distance calls.
_ Voice call: A user can place a call directly to the speaker of another user’s
telephone.
_ Volume control: The volume of the handset, speaker, and ringer
can be adjusted.
Caller ID can be provided in some key systems using one of two methods.
With analog lines, callers are identified with the ADSI protocol. Some key systems
support BRI ISDN, which is also capable of caller ID. In either case, the call identification
extends to the station display when the call is transferred.
Voice mail is readily available in key systems. Since DID is not a key system
feature, calls are either transferred to the user’s voice mail manually, or an auto
attendant prompts the caller to dial by name or extension number.
Key systems are often used across Centrex lines to provide features that
require dial-access codes on POTS telephones. Many LECs offer lines with
Centrex-like features such as transfer, conferencing, and third-party add-on. These
features are activated by sending a momentary on/off hook flash toward the central
office to signal for second dial tone. Flashing the switch hook of a key system
telephone signals the KSU to return second dial tone from the key system, not
from the central office. Therefore, most key systems provide a feature button, typically
called “flash” or “link” to flash the PSTN line. This feature is essential in any
key system that is intended to work behind Centrex. PBXs rarely provide this feature
because they are intended to interface trunk-side connections in the central
office, and these do not respond to switch hook flashes.