GE 28821 Series User Manual page 22

5. Use the touch tone pad to enter the handset number to be monitored.
NOTE: When this phone system is expanded (up to
purchase of optional Model
handsets are named HANDSET 1, HANDSET 2, HANDSET 3
respectively.
6. The receiving handset will turn on the microphone and the originating handset
will turn on the speakerphone to monitor sound from the receiving handset.
NOTE: For room monitoring mode to work, the originating handset
must NOT be on the cradle.
NOTE: While in room monitoring mode, the handsets will emit an
alert tone approximately every 5 seconds if there is an incoming
call. You may press the SPEAKER button to quit room monitor and
answer the call.
NOTE: While in room monitoring mode, the originating handset can be
switched to monitor by handset earpiece by pressing the
Switch back to speakerphone by pressing the SPEAKER button once.
NOTE: Press the
monitor mode.

TBD
END/cancel button on the handset to exit room
handset with recharge cradle),
6 handsets by
and so on
TALK button once.