Functions are additional circuits/outputs on a decoder that can control nearly anything you can think of – lights, sounds, smoke, animation, uncoupling devices, etc. Many are not limited to simple on/off functions - for example lighting functions are capable of imitating Mars Lights, Gyralites, Rule 17 dimming, single or double flashing strobes, ditch lights, and other effects. Output is generally 12 volts DC - if you want to use LEDs or low-voltage lights, you'll need to use a resistor as well. See the decoder's documentation as some have settings for LEDs.
There are currently 29 functions, F0–F28. Many Digital Command Control systems now support 29 functions, while some may still only support 13, F0-12. Function support depends on the software in the command station or throttle. Some decoders are now offering logic level outputs, which when coupled with a daughterboard in the locomotive, allow for many more functions or features to be created without a corresponding increase in outputs from the decoder.
The NMRA DCC standard doesn't define functions, but allows for features such as this.
Swiss Mapping is a temporary term created by Zimo to describe an alternate method of mapping functions to replicate the lighting used on Swiss railways.
- Swiss Mapping and other extensions of the decoder software are far beyond the capability of a simple "engine and lights" decoder. ZIMO decoders and sound decoders are for "higher" functions predestined, since most types have 6, 8, or 10 function outputs available. The impetus for the concrete development of the Swiss Mapping was part of the planned configuration for ZIMO decoders (creating CV sets and sound projects) for large and small volume manufacturers, but priority should be given for a Roco SBB Re442, which can for the first time represent all Swiss lighting variants, and which with the previous CV structure would not be possible. (Zimo Newsletter, Sept. 2012)
Zimo decoders use several groups of CVs to accomplish this. For more information consult the manuals for a Zimo decoder.