AT&T System 25 - Manual (Page 11)

Call Waiting
While you are using your phone, you may be notified through
the handset that a call is waiting. If you hear one short tone, it
is an inside call waiting for you; two short tones indicate that
you have an outside call waiting.
You must either end the existing call or place it on hold in order
to answer the call waiting.
Answering - Holding the Existing Call
1 Press the switchhook.
2 Listen for confirmation tone and dial tone.
3 Press * 9 .
❑ ❑
4 Answer the waiting call.
5 After completing the second call, press the switchhook twice
in order to return to the held call.
NOTE: If you hear dial tone,
to return to the call on hold.
Answering - Ending the
1 Hang up.
press the switchhook once more
Existing Call
2 When the telephone rings, lift the handset.
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