Dahua compact RS-485 expansion module for access control and intercom systems. The module provides additional alarm inputs and outputs, including a 12 V power output, and supports cascading of up to 20 modules. It enables the integration of external doorbell buttons into the VTO system.Key features: 8 alarm inputs or 4 alarm outputs. Ports can be configured as inputs or outputs using a 1-bit DIP switch. Integrated 12 V DC, 200 mA power output for peripheral devices. Supports cascading of up to 20 modules (maximum cable length: 100 metres). Requires a 12 V DC / 1 A power suppl