IVM includes a software detection system to attempt to accurately detect when a call has been answered. The default is set to work for as many different environments as possible, but it may need to be modified to work for specific systems. These settings can be found on the "Auto Dial" tab in the web interface.

Answer detection works by listening to the phone line and looking at the length of the voice after the call is answered. A longer 'message' indicates an answering machine has answered the call, while a short 'greeting' suggests a real person.

Because IVM can't be sure that the person who has answered the call has finished their sentence. It will wait for silence (usually about 2 seconds). This means there will always be a short delay after the person answers before the Outgoing Message will start. Also note that IVM can misdetect and answer due to messages on the line.

In all circumstances you should design your outbound menu structure to be tolerant of early detections, false detections and late detections.

Ringing silence detect time [ms]

When IVM detects a ring tone it will wait longer before starting than after voice. This time must always be a little longer than the maximum time between ring tones in your country. In the USA / Canada use 4100ms (the maximum time is 4000). In Europe and Australia you can reduce this to 3100.

Voice silence detect time [1000 - 4000ms]

After voice is detected IVM waits for a silence gap before it begins. If this is too short IVM can begin between words. A reasonable time is usually 2000ms. Be careful if you expect many answering machines because answering machine message often have longer gaps.

Ringing or busy time out [10 - 50 secs]

IVM will abort the call as being unanswered if it detects ringing or busy tone for longer than a predetermined time. A reasonable value is 15 seconds.

Answer detect fail time out [15 - 60 secs]

IVM will abort all calls as being unanswered (including those with voice detected) after a maximum time without any silence detected. 30 seconds is a reasonable.

Assume answer machine if voice longer than [secs]

If you want to play different messages to calls answered by answering machines, IVM can attempt to guess whether the voice is a real person or an answering machine based on the length of the greeting. A typical value might be 8 seconds. If it is longer than this an answering machine must be assumed.

If you expect many answering machines you should use a longer voice silence detect time because answering messages can often have longer gaps.

Note that answering machine detection is never completely accurate. You should design you menu structure to be tolerate of misdetections.