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Glossary · Call centre operations

What is ACD (automatic call distributor)?

  • Also called: automatic call distribution, call distribution system

Reviewed by Sujan ThapaliyaLast updated

Definition

An ACD is the system that receives inbound calls, holds them in queues and distributes them to agents according to rules — availability, skills, priority or business hours. It is the routing engine every contact centre runs on, whether or not anyone calls it that.
The three STIR/SHAKEN attestation levels, which underpin how acd (automatic call distributor) behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, acd (automatic call distributor) included.

In practice

How acd (automatic call distributor) actually works

The rules are where the value sits. Routing by skill means the first agent to answer is one who can finish the call; routing by priority means a support contract is honoured without a human deciding; routing by hours means nobody has to remember to change anything at five o'clock.

An ACD is also the source of inbound reporting. Service level, average speed of answer, abandonment and occupancy are all computed from what it records, which is why an inbound operation without one is guessing.

Modern platforms fold the ACD together with the IVR, the queue and the agent interface, so the distinction matters mainly when comparing products that price them separately.

Worked example

Two agents free, one caller waiting: longest-idle sends it to whoever has waited longest, skills-first sends it to whoever can finish it. Those are different answers, and the queue has to be told which one you want.

ACD (automatic call distributor): common questions

What does an ACD do?
Takes inbound calls, queues them and gives each to the right available agent, using rules rather than whoever happens to grab the phone.
Is an ACD the same as an IVR?
No. The IVR asks the caller what they need; the ACD decides which agent gets them. Most inbound lines use both, and confusing them makes routing problems hard to diagnose.
Do small teams need an ACD?
Any team that misses inbound calls does. Below a handful of people a hunt group may be enough, but the moment you need to know how many callers gave up waiting, you need what an ACD records.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

See acd (automatic call distributor) in the product

A call queue holds inbound callers in order and distributes them to whichever agent frees up next, instead of ringing one phone and failing. A callback option lets the caller keep their place and hang up, which is what actually reduces abandoned calls.

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