An ELD connects directly to a vehicle’s engine control module (ECM) via a port to monitor and record critical data. Key functions include:

• Engine synchronization: Tracks when the vehicle is running, moving, or idle.
• Automatic data capture: Records driving hours, mileage, and engine operation.
• Driver interaction: Allows manual input to classify status (e.g., 'off-duty,' 'on-duty,' or 'personal conveyance').
• Compliance checks: Generates reports for law enforcement officers during inspections.

ELDs also store data that fleet managers can access through dashboards, enabling real-time monitoring of HOS compliance, vehicle diagnostics, and route performance.