The actuator is the part of the device that moves the mechanism and makes it work, switching those numbers that you put into it. In terms of these switches, the actuator type is simply going to be the type of switch that the device uses. While they all may fall under the umbrella of the thumbwheel switch, you will find that there is quite a bit of difference when one looks at all of the different actuator types.
The basic types are the leverwheel, thumbwheel, and pushwheel. The leverwheel, as one can guess from the name, features a lever by which one can change the numbers. The thumbwheel is one that will allow you to use your thumb or a finger to make changes on the switch. The pushwheel, which is quite a popular option, has buttons that you will be able to push in order to change the numbers.
You will also find that some of the devices also feature locking options. Choosing a switch that has a locking option might be a good idea for many people. When you have the ability to lock the device, you will find that you are going to be far less likely to make mistakes and switch something accidentally. It is usually better to be safe rather than sorry.