I did not look at the page that Leejor suggested, but I am guessing that he too is sending you to the page that describes what I am to write -
The connection time is a combination of factors depending upon when you start to measure. One if these is the amount of time that it takes the 3CX system to process the request and send it out your desired route (Patton in this case). The next is the amount of time that it takes for the provider to receive, process, negotiate and then route the request to the desired end-point. The end-point may also play a significant factor depending upon if it is international or has other switching aspects involved to reach its destination.
With regard to the Yealink, or most SIP phones, it is similar to dialing with a cell phone in that the dial string is captured so to speak, not live, and the send key is the signal to indicate that you have input all desired digits. The phone by itself has no advance way to know if you want it to dial with 7, 10, 11, or more digits, so it requires input from the user to tell it when to initiate the dial sequence.
Most of the phones have a timeout such that if no digits are added to the string within a defined time period (Yealink is generally defaulted to 4 seconds), then the phone will automatically assume that all is well and will initiate dialing. You can alter the setting to suit your need.