Dialer Detection Issues
There can be significant differences in the timing and quality of detection of call outcomes from one geography to another, and from one signaling system to another.
Pre ISDN
Traditionally, call centers using analogue lines have had little help from the call outcome information provided over the PSTN. In many cases all the onus was on the dialer not just to distinguish among different call outcomes e.g. live voice from answering machines, but also to distinguish these from busies and the variety of other telco outcomes. Some call centers, especially smaller ones, are still using analogue lines. The detection technology available to them has improved substantially in recent years. Even so, most dialers will fall short of detecting all outcomes successfully.
What this means in practice is that some live calls may well be screened out by the dialer and dropped. Effectively they are abandoned calls. A dialer may not be aware that it is doing this, unless of course the called party realizes what is happening and calls into complain.
Oceanic® does not make allowance directly for any abandoned calls of this type. But if you want to allow for them, you can classify them as either additional busies or other telco events, and remember you have done this, when you do call recycling. Don't put them in your abandoned call target!
Post ISDN
In many countries ISDN has been strongly promoted as the way forward for call centers, for reasons including price and service quality. Another advantage that it should bring is a string of (digital) event codes with information about busies and other telco call outcomes, meaning that a dialer only has to distinguish between people and machines. We say 'should' because not all ISDN implementations are alike, and some may fall short of providing full information on busies and other telco call outcomes.
When ISDN does screen out busies and other telco events, then if dialer detection is implemented, virtually all faxes and modems should be screened out in a fraction of a second, using frequency detection. Which leaves a shootout between live voice and answering machines.
For more on this, see Answering Machine Detection and Answering Machines - The Good News.