Panasonic KX-T336 System Reference Manual page 293

Deleting the ATLC card will be an error if there exist the following assignments:
9 "Trunk Group (TGl)",
Incoming Mode (Day) is set to "1 (ATT)."
intercept Routing (Day) is set to "A (ATT)."
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"Doorphone (DPH)",
Doorphone Assignment is set to "A(ATT)."
Deleting the DISA card will be an error if there exist the following assignments:
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"Trunk Group (TGl)",
Incoming Mode (Day) is set to "4 (DISA)."
Incoming Mode (Night) is set to "4 (DISA)."
Deleting the HLC, SLC, LCOT or GCOT card will be an error if there is the
following assignment to the slot to be deleted:
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"Power Failure Tansfer (PFT)"
See Section 1-A-5.00 "Service Cards Description" for installing the cards in
combination.
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