VTech 15200 User Guidance page 31

Steadily on when the speakerphone is turned on.
Steadily on when the answering machine (TAM) is
turned on.
Steadily on when there are new and unread voicemail
messages.
Steadily on when the handset booster is activated.
Press to initial an intercom call when idle.
(INT)
Press to go back to previous menu level or cancel the
current action if applicable.
(BACK)
Press to clear a character or stop the alarm if
applicable, press to mute / unmute during a call.
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