AT&T 8503T - Manual (Page 11)

[feedback tone] The tone that appears in brackets directly across from a
procedural step indicates what you should hear from your
handset after successfully performing that step.
Feedback tones may also be included in the bullet listing
of resulting light indications and tones after an individual
step has been completed.
For a list of tones and their meanings, see the section titled Tones and Their
Meanings.
Quick Reference Lists
At the end of this booklet is a set of quick reference lists. Use them to record your
feature and trunk codes, Abbreviated Dialing personal list items, and message and
attendant extensions. Once you have completed the lists, remove the page from the
booklet (tear along the perforation), and keep the lists near your voice terminal.
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