ACD (Automatic Call Distribution) is a system that automatically routes incoming calls to available operators based on predefined rules in a call center. It is a core technology that directly affects call center efficiency and customer satisfaction, working alongside PBX, IVR, and CTI to form the backbone of phone support.
ACD routing algorithms come in four main types. First, longest-idle-agent routing, which prioritizes the operator who has been waiting the longest, equalizing workload. Second, skills-based routing, which matches calls to operators based on language ability (Japanese, English, Chinese), specialty (technical support, billing, cancellation), or qualifications (financial product licensing). Third, priority-based routing, which gives precedence to VIP customers or high-urgency inquiries. Fourth, percentage-based routing, which distributes calls across multiple sites or teams at set ratios.
ACD works closely with IVR. After IVR directs callers ("Press 1 for technical support, 2 for billing inquiries"), ACD selects the optimal operator from those with the matching skill set. When integrated with CTI, customer information appears on the operator's screen the moment the call connects, enabling smooth handling.
Key KPIs for ACD management include answer rate (the share of incoming calls that were answered), average speed of answer (ASA), and service level, which pairs a response time with a percentage, as in "answer 80% of calls within 20 seconds." Target levels vary with the size of the center, the industry, and any SLA agreed with customers, so they are better set against your own historical figures than borrowed from an industry rule of thumb. Monitoring these KPIs in real time and adjusting operator staffing and routing rules is a primary responsibility of call center managers. Cloud PBX services often include ACD as a standard feature, with browser-based rule changes and real-time monitoring. See Call Center Quality Tips for operational best practices.