An ACD is an automated call distribution system (otherwise known as an automatic call distributor). ACDs distribute calls. Think of them as an automatic switchboard that constantly checks to see what agents are available and what agents are qualified to handle incoming calls. The switchboard then connects calls to qualified (and available) agents. Here's how Lucent (the OG of call center software) defined ACD years ago: An ACD is the part of a telephone system that recognizes and answers incoming calls and completes these calls based on a set of instructions contained in a database. The ACD can send the call to an operator or group of operators as soon as the operator has completed a previous call or after the system has played a message to the caller.