CUCM interdigit timeout is the time that you have between digits that you dial. Suppose that Cisco CUCM interdigit timeout is configured as 3 seconds. This means that, when you dial a string of 6 digits, you have at maximum 3 seconds between each two digits you dial. And with patterns that have undetermined length such as international numbers, with the last digit you hit, interdigit timeout kicks in and you have to wait 3 seconds after the last digit.
What if I don’t want to wait that extra 3 seconds at the end of the string I dial? The common mortals will tell you “dial the pound key at the end of the digit string”. Ok but is the pound key a supported command on CUCM?
The answer is “no”. The pound key (#) is a mere character. It is not a special macro. It’s just a character. But in CUCM, we can associate it with the concept of Interdigit Timeout by configuring the Route Pattern with a pound key “#” at the end.
In fact, when you have a route pattern in the form of ABCD#, and there are no potential matches (PotentialMatches is empty), then ABCD# route pattern is unique and is immediately routed/blocked. This ensures that each time you don’t want to wait for the interdigit timeout to expire at the end of the digit string, you can press the pound key and send the digits to the call control system (CUCM or CUCME).
Given that, we will have a sort of repeated patterns: ones with the pound key and ones without. That’s fine, as long as each pattern exists in its two forms, because some users will dial the pound key and some won’t. We need to make all users happy don’t we?
Interdigit timeout in Cisco CUCM 8
In Cisco gear, the interdigit timeout is called T.302 timer. Here are some values to know:
These values are in milliseconds (msec). If you have worked with gateway redundancy protocols such as HSRP and VRRP, you will notice that timers in milliseconds provide great granularity and flexibility.
As mentioned in the table, the default interdigit timeout value on Cisco gear is 15 seconds. And it can be changed as we will see in the following paragraph.
By the way: did you know that, as soon as you lift the handset, there is another timer that kicks in? In fact, the T.302 Timer does not execute before the first digit you enter. So this special timer is called the Off-hook to First Digit Timer. It’s simply the amount of time the call routing component wait for you to dial your first digit. This is marked by the continuous and often annoying tone that you hear before dialing a number.
How to change interdigit timeout on CUCM
Changing the default value of the interdigit timeout is easy.
- In Cisco Unified CM Administration menu, go to System –> Service Parameters
- From the drop-down menu, select your preferred server
- In the list of services, choose the “Cisco CallManager” service
- You will be presented with a big list of services. Unless you are a CUCM hero, you will read the menus line by line. I recommend you press CTRL-F, then type “T302 timer” in the search field.
- Once you are at the T302 level, change the default value with the desired one
- Click Save
At this point, you need to restart the Cisco CallManager service.
To do that:
- In the navigation menu, select Cisco Unified Serviceability from the drop-down menu and click
- Go to Tools –> Control Center –> Feature Services
- Select your server
- Select the radio button in front of the CallManager service
- In the upper menu, click on the Restart button