How do I factory reset a Linksys (Sipura) SPA?

How do I factory reset a Linksys (Sipura) SPA?
To return the Linksys (Sipura) SPA to an unconfigured state:

1. Pick up the handset attached to your SPA device. You may or may not hear the dialtone.
2. Dial ****73738#
3. Dial 1# to confirm.
4. Hang up.

The device will reboot with a factory-default configuration. All previously entered configuration settings will be removed.

It is possible for service providers to restrict access to this feature. If you are using a SPA that has been provisioned by a provider, you may need the assistance of the service provider in order to perform this action.