Hot Dial is a feature where the user lifts up the handset (offhook) and the phone automatically initiates a call to a predetermined number, e.g. in airport lobbies, emergency calls or in similar single scenario situations. There are two different approaches how this can be achieved.
Configuration via Auto Dial Setting
The setting auto_dial and auto_dial_target allow for a scenario where once the user either lifts the handset or presses any line or number key, a predetermined number is dialed immediately without delay. The following values have to be set:
Configuration via Action URL
Hot Dial can also be achieved by using an Action URL. However this approach limits the Hot Dial behavior to the Offhook event while the auto dial setting approach triggers on several more events.
The outgoing call is triggered using the phone's Action URL on offhook. (Action URLs are HTTP GET requests that are issued when a specific event occurs on the phone.)
You need to set the actual IP address of the phone and your destination number and once the phone goes offhook the ACTION URL is triggered.