Panasonic KX-T336 System Reference Manual page 128

Conditions
Held Call Reminder
If these items are programmed however "System-Operation" Held Call
Held Call Reminder (ATT)
Reminder is not set to "Yes," Held Call Reminder does not function.
Function
The following functions appear on the function line of this setting screen.
COMMON (SHOW LV, CHG LV, INS, OUS, REMOVE, EXIT) and HRD CPY keys
are available in this setting screen.
For operation, refer to Section 7-i "Operation of Function Keys."
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