Panasonic KX-TCD535HK Operating Instructions Manual page 14

Display
Base Unit Display Icons
H/set 1
IN USE
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14
Intercom/Paging
Making or Answering calls
Call Bar ON
Phonebook Mode
Ringer Volume OFF
New call (Caller ID only)
The line is being used by another unit.
---IN USE---
Intercom Mode
Cordless Handset Name
H/set 1
(e.g., Cordless Handset 1)
Voice Mail