Lucent Technologies PARTNER Advanced Communications System Programming And Use Instructions page 262

To transfer a call to a Hunt Group:
1. While on a call, press the switchhook down once rapidly.
You hear intercom dial tone.
7 7
2. Dial and a group number (1–7).
The next available extension in the Hunt Group rings. If no one answers
within three rings, the call hunts to the next available extension. However, if
Transfer Return Rings is programmed for less than four rings, the call
returns to the extension that transferred the call, or to that extension's
transfer return extension.
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Feature Reference