A dimmer rack module is a small device that is used in professional lighting to adjust the brightness of a light fixture. It works by altering the voltage of electricity that is delivered to the lamp. When the dimmer rack module reduces this power, the brightness of the lamp will fade down (become dimmer). Alternatively, if the dimmer rack module increased the power, the lamp will fade up (become brighter). Interestingly enough, a dimmer rack module allows for minor color control as well.

Although large dimmer racks are sometimes used, these are often replaced with a dimmer rack module, which is smaller and contains a 20 to 50 ampere breaker. The advantage of a dimmer rack module is that it can also supply current to other devices, such as foggers and hazers, or lifting equipment. This is important as these other devices can be damaged if you fail to use a dimmer rack module on non-dimming electrical devices. The circuit to which a dimmer rack module is connected to will be constantly energized, thus protecting these other devices. Even in cases where it is thought that a regular dimmer rack will always be operating at full power, it can be dangerous for non-dimming devices due to interruptions in the data stream caused by DMX signals and noise interference, which would lead to the dimmer dimming the circuit.