Wholesale voice
ACDAlso known as Average Call Duration, Average Length of Call (ALOC)
Definition
ACD (Average Call Duration), also called ALOC (average length of call), is total billed minutes divided by the number of answered calls. Together with ASR it is the main indicator of voice route quality: healthy routes carry real conversations, while unusually short ACD suggests dropped calls, poor audio or false answers.
How ACD is calculated
ACD = total billed minutes ÷ answered calls. A route with 450 answered calls totalling 1,575 minutes has an ACD of 3.5 minutes (3:30). Unanswered attempts are excluded, which is what separates ACD from ASR.
Use the same billing basis consistently. Rounding to 60-second increments inflates ACD compared with per-second billing.
Reading ACD
ACD is most useful as a trend: plotting it per route, per hour and per day reveals problems as soon as they start rather than at month end.
| Pattern | Possible cause |
|---|---|
| ACD falls suddenly on one route | Call drops, one-way audio or poor quality making people hang up |
| Very short ACD with normal ASR | Calls answered by announcements, voicemail or false answer supervision |
| ACD differs by device or SIM | Signal, handset or network problems on specific lines |
ACD also varies naturally by traffic type: contact-centre calls, retail calling cards and business calls each have their own typical range, so compare against a baseline.
ACD in GSMCalls
Averages hide detail, so look at the distribution as well. A route whose calls cluster at a few seconds, or at exactly the same length, deserves investigation even if its overall ACD looks normal. Many operators track the share of calls under 30 seconds alongside ACD.
GSMCalls computes ACD alongside ASR, minutes and revenue per site and device from its CDRs, so a device with a collapsing ACD stands out quickly. See platform and telecom billing.
Frequently asked questions
What is the difference between ASR and ACD?
ASR is the share of attempts that are answered; ACD is how long answered calls last on average.
Is ACD the same as ALOC?
Yes. Average length of call (ALOC) is another name for the same measure.
Does ACD include ringing time?
No. ACD is based on billed, answered duration only; ringing and set-up time are measured separately, for example by PDD.