From Zenitel Wiki
ABSD = AlphaCom Billing Service Daemon
A AlphaCom can host a ABSD process for billing services. ABSD requires a license to be inserted, and the application it self runs from local flash filesystem. ABSD handle the realtime authorization and charging of outgoing calls. Configuration and invoicing is handled by a BillingWeb application.
The ABSD software communicates with the local AMCD using Stentofon Simple Link Layer. The ABSD software is defined as device number 198, and connects to local AMCD on TCP port 127.0.0.1/40002. In AlphaNet, remote AlphaComs communicates with ABSD via the hosting AMCD using the normal AlphaNet routing.