This is only applicable to Analog lines. When the channel sets are "linked", Abacus will reference to the own phone book of the calling party for the relevant caller ID information. However, when the channel set is not "linked", Abacus will reference to the external phone book of the terminating party for the information. Note that when AFT (Analog Feature Testing) is used, the channel set is considered as "linked", hence the own phone book of the calling party will be used.