Difference Between PBX and ACD (With Table)

PBX systems are now utilized to connect contemporary SIP (session initiation protocol) and IP phones. the Automatic Call Distributor (ACD) enhances the caller experience by simplifying communication. It helps in preventing call systems from being overwhelmed. It also helps in preventing callers from becoming caught in a call loop.


The main difference between PBX and ACD is that PBX stands for Private Branch Exchange which allows employees of a big organization to receive and make calls without relying on the switching routing services of the phone provider. ACD stands for Automatic Call Distribution and it connects the company’s internal resources with outside callers.

For the agents to work with their supervisor or another agent to service the client appropriately, the PBX includes numerous team collaboration solutions such as screen sharing, Some of these capabilities, such as call transfer or screen sharing, can be performed by agents without the knowledge of the consumer on the line.

ACD distribution is based on pre-defined principles that are particular to the company’s configuration or requirements. calls on holiday are automatically sent to voicemail, but calls received from numbers with certain prefixes may be directed to agents who can help callers in specific languages or who are familiar with a specific location.

Comparison Table Between PBX and ACD

Parameters of ComparisonPBXACD
Full formPrivate Branch ExchangeAutomatic Call Distribution
FunctionA PBX allows employees of a big organization to receive and make calls without relying on the switching and routing services of a public phone provider.  The automatic call distribution system (ACD) connects the company’s internal resources with outside callers.
Traffic jamIn a PBX system, traffic congestion may develop.In the ACD system, there will never be a traffic jam.
CapacityLess number of linesMultiple calls can be handled at once, and the source is identified.
Real-time reportingDoes not includeIncludes real-time reporting

What is PBX?

The term “Private Branch Exchange” stands for “Private Branch Exchange.” A PBX is a phone switch with customized software that is located at a specific corporate location. Both external and internal communications are handled by the PBX. The PBX is equipped with signaling that is particular to the phone company, such as busy signals, dial tones, ringing, and so on. They can also include features like call forwarding, usage statistics, and phone conferencing. PBX-like applications can be created using a PC-based Key system or telephone system. Manufacturers occasionally provide ACD software as an add-on program on their PBXs to improve the functionality.

The PBX is the “machine” that directs incoming calls, allows a company to transfer calls to different extensions, and stores all of the requirements for how a business phone system should function. The PBX can either employ telephone hardware to make the calls or a computer-integrated telephony or softphone system to make the calls. A cloud PBX is a hosted communications system that offers the same private branch exchange capabilities as an on-premise PBX without the additional expense of infrastructure administration.

Time and technology, on the other hand, have altered the consumer telephony environment, with the Open-Standards-based IP PBX serving as the flag-bearer.

What is ACD?

Since the 1950s, when PBX equipment routed calls using switchboard principles, many iterations of the ACD have existed. The Rockwell Galaxy Automatic Call Distributor, which used technology based on a method invented by Robert Hirvela, introduced it into widespread usage in the mid-1970s. Continental Airlines installed the Rockwell ACD in 1973 and used it for almost 20 years.

The abbreviation “ACD” stands for “Automatic Call Distribution.” ACD is a switch as well as an application. It is in charge of accepting, holding or queuing, delivering, and reporting high-volume phone calls. Delay announcements, CRT displays that show delay data and indicate incoming calls, headset operations, and so on are some of the extra elements of ACD.

There are two types of ACDs: freestanding and C.O. (central office) based ACDs. Supporting highly specialized systems with stand-alone ACD is beneficial. It has features like monitoring, real-time reporting, and sophisticated routing systems. Statistics are collected by a stand-alone ACD. An auxiliary processor is included in this program, which collects and reports all statistics. Because ACD handles so many calls, it has a system specialized to call processing.

The major advantage of C.O.-based ACD is that it offers all of the capabilities of an ACD/PBX without the need for a switch.

Main Differences Between PBX and ACD

  1. “PBX” stand for “Private Branch Exchange” and “ACD” means “Automatic Call Distribution” .
  2. A PBX allows workers of a large business to receive and make calls without the need of a public phone company’s switching and routing service, whereas an ACD connects the company’s internal resources to outside callers.
  3. Because fewer lines are coming in, the PBX can manage less BHCA (busy hour call attempts). Traffic jams can develop in a PBX system, but an ACD can handle multiple calls and identify the source of the call, and the voice-automated system assists in determining the true purpose of the call and connecting it to the appropriate agent, thereby decreasing traffic jams.
  4. PBX does not have many features whereas ACD is a more sophisticated system that includes monitoring capabilities, real-time reporting, complicated routing systems.
  5. PBX is inefficient, but ACD offers a precise call routing system and ensures higher customer satisfaction.


The Automatic Call Distributor (ACD) is a telecommunications system that, depending on distribution criteria, answers calls and sends them to specified departments or agents inside an inbound call center. It improves caller experience by streamlining communication, preventing call systems from being overloaded, and ensuring that callers do not become stuck in a persistent loop or backlog for an extended period.

Telephone networks for businesses have progressed. Users may connect to other desk phones without relying on an operator or switchboard thanks to one of the earliest advancements. Modern SIP (session initiation protocol) and IP phones are now connected through PBX systems. VoIP systems are another name for them. Users can also use the internet or a mobile app to access their workplace phone extension.


  1. http://tarrani.net/mike/docs/TrafficEngineering.pdf
  2. https://ieeexplore.ieee.org/abstract/document/8631894/

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