A 4 Channel xP Module such as an xpBD4 appears to reserve 8 channels in Security Expert
EcoStruxure Security Expert
xP Expansion Modules
xP Expansion Modules were originally created for the Continuum Access control system but through transitions are now being used with Security Expert as well. When used in Continuum, a 4 digital channel xP Module would reserve 4 channels only. However under Security Expert that same 4 digital channel xP Module will reserve 8 channels instead.
Continuum ACX5740 plus xPBD4 plus xPD18
|ACX5740||Inputs 01 -12||First 12 channels|
|xPBD4||Inputs 13 -16||Next 4 channels|
|xPDI8||Inputs 16 - 24||Next 8 channels|
Security Expert SP-ACX plus xPBD4 plus xPD18 (Note all SP-ACXs have ACX 5740 I/O counts)
|SP-ACX||Inputs 01 - 12||First 12 channels|
|xPBD4||Inputs 13 - 20||Next 8 channels|
|xPDI8||Inputs 21 - 28||Next 8 channels|
Some of the channel reservation under Security Expert has changed relative to how it used to be handled in Continuum, so now even for a 4 digital channel xP module such as an xPBD4, 8 Channels are automatically reserved by design even if only 4 of those channels are actually used.
To check all Input, Output, Digital and Analogue xP Channel reservation scenarios under Security Expert please refer to AN 310 Security Expert - xP Module Configuration - Application Note (for this digital input example, page 7 shows the relevant channel assignment).