There are several ways to create a system-wide speed dial number in FreePBX:

1. Create an outbound route. In the dial pattern rules, set the speed-dial number as the prefix. Set the actual number to dial as the prepend. This method has the advantage of allowing you to use the outbound routes caller-id feature to set a specific caller ID for calls made to the speed dial number and to choose which trunks to use when calling that number.

or

2. Create a Misc Destination, then put the number you want to call (with # suffix if it's an outside number) in the dial: text field, e.g. 18005551212#. Then create a Misc Application, put the extension or speed dial number you want to use in the Feature Code: text field, and make the Destination the Misc Destination that you just created.

So you call the number you specified in the Misc. Application and it routes to the destination you specified in the Misc. Destination. This keeps everything within the FreePBX interface. Also, you can specify the Misc. Destination from anywhere in FreePBX that you can select a destination, such as from an IVR menu (if that is ALL you want then you don't even need to create the Misc. Application).

or

3. Create a Ring Group with only one number in the group, that being the number you want to call (with # suffix if it's an outside number); then the Ring Group number becomes your speed dial number. While that method probably uses slightly more processing time on each call, it does give you the ability to use the options associated with Ring Groups (such as specifying the amount of time to allow the call to ring, or playing Music on Hold instead of a ringing signal to the caller). Perhaps more significantly, if you set the Ring Time to a shorter time than the called number's voicemail timeout, you can have unanswered calls go to your FreePBX voicemail (or to another FreePBX extension or some other destination of your choice) rather than the called phone's voicemail, if that's what you'd prefer.