Panasonic KX-NS500 Features Manual page 435

Explanation:
As shown in the CDPG table above, CDPG 1 consists of Port 1 of the first card and Port 1 of the second card.
When "1023-456-7890" (leading number: 10) is dialled:
The leading number (10) is
searched for in the Hunt Pattern
Table.
CDPG 1 is the 1st priority
CDPG.
If all the ports belonging to CDPG 1 are busy, the call is rerouted to the lowest-numbered available port
belonging to CDPG 4, which is set as the second priority for this leading number.
The call is routed to
Port 1 of the first card.
Port 1 of the first card
is busy.
4.3.2 Voice over Internet Protocol (VoIP) Network
The call is rerouted to
Port 1 of the second
card.
Port 1 of the second
card is available.
The call is
answered.
Feature Guide 435