Assuming that you are using the Advanced mixer...
- From the Main Deviation menu, select the model icon, to enter the Mixer menu.
- Select the channel button (on the left side of the mixer screen) for the channel which you want to set the safe value.
- On the menu that appears, the fourth item down is the safe value "spin-box". You change the value by selecting the arrows on either side of the displayed value. The left arrow decreases the value, and the right arrow increases the value.
- Note that the full scale range for most signal inputs are from -100 to +100, not 0 to +100, so -100 is actually the minimum value. For instance, if you are trying set a throttle hold value, -100 is low throttle, and zero would actually be half throttle (unless you are have changed the scaling).
This is covered in section "8.2.2 Channel Configuration" in the User manual (on Page 30).