AudioCodes 450HD - Basic Phone Operations; Making and Answering Calls

Administrator's Manual 5. Configuring VoIP Settings
Version 3.4.3 77 400HD Series IP Phones
Parameter Description
voip/dialing/allow_calling_self_extension/
enabled
If disabled (default), calling the self-number (user ID)
will be blocked.
If enabled, the phone will send the invite although it is
for its own extension. (In some proxies this is how you
access voice mail).