Trimmer resistor adjustment tools are used to alter the resistance on a trimmer resistor, a type of potentiometer which is usually set to a given value and then is kept in that position. Potentiometers control the level of electric potential, or voltage, in electronic equipment. Adjustment tools are generally only used when the equipment is being installed or serviced, as the values set on installation should already be correct for the function of that device.
Trimmer resistors are mounted directly onto circuit boards and set to a particular resistance using a trimmer resistor adjustment tool via a screw on the device. They may then be held in place using a fixative device. General users are not usually able to access the trimmer to move it.
Trimmer resistor adjustment tools may vary slightly in design depending on the type and design of trimmer they are intended for use with. Many of this type of tool will work with a range of trimmers.