A dummy extension is where you create an extension, but there is no phone attached. You then set the forwarding rules to send the call to the desired "dial and external number" where you then populate the field with the number desired to be dialed.
When one dials into the system and the IVR answers. you enter in the extension for which the external number you wish to reach is set. As there is no extension, this results in the rule for "phone is busy or unregistered" being invoked.
There are a couple of downsides to consider:
1. Anyone who accidentally enters in the extension during the IVR action will also be directed to the number...so pick extension that are less likely to be accidentally dialed.
2. You will need a dummy extension for each external number desired.
As mentioned earlier, you could also set the IVR so that it transfers you directly to your voice mail whereupon you can then dial out directly.....provided you have the option checked in "settings, global options".
The IVR will allow for direct input of an extension number at any time during its operation. It is merely a convenience as it " announces" destinations so that the caller can press a single digit and get directed to an extension that might not be known to the caller and could be comprised of up to 5 digits. Because the IVR uses a single digit input (0-9), there is no issue as all extensions must be at least 2 digits.
