Panasonic KX-T336 System Reference Manual page 334

Conditions
When "+++"s appear, they cannot be assigned.
The "Type" and "Number" of the DN-01 (fixed to PDN) is set automatically.
The "Number" displays the number assigned to the DN in "DN Assignment (DNA)."
Up to three PDN buttons can be assigned consecutively to DN-01 button through
DN-3 button.
PDN buttons must be consecutive. For example, it is not possible to program as
follows:
PDN SDN PDN
(DN buttons on PITS 7000 series)
DN-XX Type
(Dv, buttonsan PITS type 20,30 and 50)
If "PRV-CO" (Private CO) is selected, a physical number of the selected
CO line must be programmed in "Number."
The CO line of the physical number belongs to a "CO Line (COL)", Trunk
Group.
The trunk group where the CO line belongs must have "Trunk Group 1
(TGl)", Type assigned to "4 PVL (Private Line)."
If "Single CO" is selected, a physical number of the selected CO line must
be programmed in "Number."
The CO line of the physical number belongs to a "CO Line (COL)", Trunk
Group. The trunk group of the CO line must have "Trunk Group 1 (TGl)",
Type assigned to "1 (ODD)" or '2 (FEX)" or "3 (WATS)", or "5 (PBX)" and
also "Trunk Group 2 (TG2)", CO Appearance Type assigned to "1 (Single
CO) .I'
If "Group CO" is selected, a trunk group number must be programmed in
"Number."
The programmed trunk group must have Ytunk Group 1 (TGl)", Type as-
signed to "1 (DOD)" or "2 (FEX)" or "3 (WATS)" or "5 (PBX)" and also
"Trunk Group 2 (TG2)", CO Appearance type assigned to "2 (Group CO)."
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