AT&T MERLIN LEGEND Release 4.0 Feature Reference page 535

Feature Reference
An SA button can have one of three attributes:
Ring. Button is used to make and receive inside and outside ringing
calls.
Voice. Button is used to make and receive inside and outside calls. An
inside call made on this button is a voice-announced call. If the person
receiving the call has a speakerphone and it is not already in use or
disabled by having Voice Announce to Busy turned off, the call arrives on
the speakerphone. Both parties hear a beep and the called person hears
the caller's voice over the speakerphone. Since voice-announced calls
cannot be made to single-line telephones, a call made on this button to a
single-line telephone is a ringing call, even if the single-line telephone
has a speakerphone.
Originate Only. Button is used only to make inside and outside calls.
Calls are not received on this button. Its purpose is to ensure that the
user always has a button available to make or transfer calls, establish
conference calls, answer call-waiting calls, or pick up parked calls. The
button can be programmed for either Ring or Voice operation for inside
calls.
The default attribute for all SA buttons (including Shared SA buttons) after the
factory settings by telephone type is Ring. The factory setting for Automatic Line
Selection (ALS) is a sequence of SA buttons. Ringing for all types of SA buttons
is set by default to Immediate Ring and can be changed to Delay Ring or No
Ring (see "Ringing Options").
Shared SA Buttons: Hybrid/PBX Mode
Each SA button (whether Ring, Voice, or Originate Only) assigned as a factory
setting or through centralized telephone programming is identified with a
specific extension. To allow two or more telephone users to join in each others'
conversations and answer each others' calls, Shared SA buttons can be
assigned. In a shared arrangement, the SA button identified with the extension
is the principal (or primary) button. Up to 16 other multiline telephones can have
Shared SA buttons corresponding to the principal extension. A telephone can
have up to 27 Shared SA buttons for other extensions but can have only one
Shared SA button for a given principal extension. (One of the first 10 buttons
must be an SA button.)
The green LED next to a Shared SA button behaves in the same way as on the
principal extension. When the principal extension or any Shared SA button
corresponding to it is busy on a call, the LED is on at the principal extension
and at all Shared SA buttons for that extension. When a call arrives at the
principal extension, that extension rings and the LED at its SA button flashes. All
telephones with corresponding Shared SA buttons also ring, and the LED at the
Shared SA button flashes.
System Access/Intercom Buttons
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