The AM4-E5 is an optional A-BUS module for the ACA-E5 controller that adds four subzones to the system. These subzones support A-BUS keypads and share a source with the main zone but have independent room control for power and volume.

The ACA-E5 hosts one or two AM4-E5 modules. Each AM4-E5 supports four A-BUS keypads (A-K3, A-K5L or A-KP2) with RJ45 ports for CAT-5 connection to keypads. Subzone keypads are typically located in rooms near each main zone. Speakers in these subzones connect directly to the A-BUS keypads with standard speaker cable.