ASR (Average Seizure Ratio) and ACD (Average Call Duration)

ASR - Average Seizure Ratio

The ratio of Successfully Connected Calls to Call Attempts. 

Usually, shown as a percentage (%), the formula is:   Successful (answered) Calls / Calls attempts * 100.  

The acceptable level (%) ASR depends on the type of voice traffic you are passing, and your goals in terms of revenue and traffic statistics.  It is generally understood that carriers with very low ASRs (~20%) have high volumes of calls that fail, and therefore calls that consume infrastructure resources, but with no (or very little) revenue.   As such, higher ASRs generally equate to higher revenue/margins.  If you are experiencing low ASR statistics, you will generally see a low ACD (Average Call Duration) - often caused by high volumes of calls from Outbound Call Centers (See below).   Your Sippy Switch does not typically affect ASR

More information can be found at:
Understanding Answer Seizure Ratio (ASR)

ACD - Average Call Duration

The Average Call Duration (ACD) is the average length of all successful (answered) calls that pass on your Switch.  ACD may change during peak periods (such as holidays where people leave many short voicemails) or if your customer(s) are passing a high degree of call center traffic (most likely if ACD remains constantly low).

Usually, measured in seconds, the formula for ACD is:     Total duration, seconds (answered calls) / Total number of answered calls.

If you are providing retail solutions, you may expect to see an ASR of 480 seconds (8 minutes), typically wholesale SIP carriers will expect to see around 300 seconds (5 minutes) whereas call centers may only expect to see 60-120 seconds (1-2 minutes).   Lower ACD is generally lower profit and extremely low ACD is symbolic of call centers.  It may be hard to find vendors (*routes) that will accept ultra-low ACD.