Function decoders are decoders for non-driven vehicles, i.e. those without connections to a motor, but with connections for function outputs. They are usually cut-down from loco decoders (as shown in the above table by "based on ..." ). have less functionality but share many of the properties of the base decoder.

This relationship with loco decoders simplifies the process of development and manufacture, and is quite useful as certain high-function decoder control logic is retained, for example to switch the lights according to the direction of travel, and at the same time as in the loco decoder. Servo-control and other useful things are taken from the loco decoder.

ZIMO Function Decoders offer even more: the second programmable address, which allows the function decoder to respond to an alternate address, which is normally set to the same as the main loco address. Thus, for example, the lighting on the train can be switched on using the loco address which will switch all the lights, or individual cars can be switched on and off using the "normal" address of the decoder.

The ZIMO High Frequency Feedback for programming and reading operations on the programming track is available in all ZIMO decoders, but is especially beneficial for for function decoders, because there are often only LEDs connected and, when programming them in service mode, there is not enough load to produce "normal" feedback.