AT&T System 25 - Manual (Page 69)

confirmation three short tones indicating that an
tone action was accepted.
coverage
DDC
DGC
DSS
data call (from
telephone)
dequeueing tone
exclusion
extending calls
FPDC
fast busy tone
feature that allows individuals to have their
calls answered by someone else.
(Data Dial Code) extension number
assigned to a data terminal.
(Direct Group Calling) a group of
telephones where incoming calls are
distributed among the group members.
(Direct Station Selection) button containing
an extension number or an access code, and
programmed by the System Administrator.
(For buttons that you can program, see
FLEX DSS.)
feature that allows you to place a data
call from your telephone, then transfer the
call to your data terminal.
three short tones indicating the
feature can now be completed.
feature that allows you to keep
listening in on a conversation.
Callback
others from
procedure followed by the attendant when
sending a call to the desired party.
(Floating Personal Dial Code) a number
associated with a person, but not a
particular telephone. FPDCS provide the
convenience of receiving calls at various
telephones.
repeating on/off tone indicating that the
dialed number or access code is busy,
misdialed, or restricted, or that an outgoing
line is busy. (Sometimes called reorder
tone.)