With AC motors on 2-rail track you should use the following decoders:

6080 - for most HO locomotives with AC motors, range of 80 addresses/one auxiliary function.

6603 - DELTA decoder with 15 addresses/no function control.

6095 - 1 Gauge decoder which can be set to either AC or DC, 80 addresses/five functions.

With DC motors on 2-rail track you should use the following decoders:

6081 - for most HO locomotives with DC motors; full range of 80 addresses/one auxiliary function.

66913 - Smallest decoder originally made for HO with DC motors and limited space. It will also fit into most N scale locomotives; 15 addresses/no function.

65853 - Maxi decoder for DC ironless core "can" motors; 15 addresses/no function control. Also suitable for LGB locomotives.

6095 - 1 Gauge decoder which can be set to either AC or DC, 80 addresses/five functions.

With AC motors on 3-rail track you should use the following decoders:

6080 - for most HO locomotives with AC motors, range of 80 addresses/one auxiliary function.

6603 - DELTA decoder with 15 addresses/no function control.

6095 - 1 Gauge decoder which can be set to either AC or DC, 80 addresses/five functions.

With DC motors on 3-rail track you should use the following decoders:

6081 - for most HO locomotives with DC motors; full range of 80 addresses/one auxiliary function.

66913 - Smallest decoder originally made for HO with DC motors and limited space; 15 addresses/no function.

65853 - Maxi decoder for DC ironless core "can" motors; 15 addresses/no function control. Also suitable for 3-rail O gauge locomotives.

6095 - 1 Gauge decoder which can be set to either AC or DC, 80 addresses/five functions. Also suitable for 3-rail O gauge locomotives, but requires more space.

61253 - DC decoder orignially used for the Märklin Köf HO model.

64001 - DC decoder orignially used for the Märklin Glaskasten HO model. This decoder has an extra output for lighting coaches through current conducting couplers.

Decoder Functions
All but one decoder have some auxiliary functions they can control. With most HO decoders there is currently only one function available, but it is separated into two functions by the direction of travel. It can be connected to the locomotive lights which would then be activated according to the direction of travel, or it can be connected to other functions such as smoke generators, TELEX couplers, motors, sound units, electro magnets, etc. In most Märklin locomotives the function controls the lights. Locomotives with TELEX couplers have both function wires connected to the TELEX which is then activated with the "Function" button on the Control units.

In cases where other function options are chosen, it will usually be found that the lights are either connected directly so they always stay on, as is the case with TELEX couplers, or they are connected along with the function to operate at the same time. This latter option is usually the case with smoke, which allows the operator to know when the smoke unit is on or off. Care needs to be taken when operating TELEX with the function option, since the TELEX couplers should not be left on for long periods of time. After uncoupling, remember to turn the function off. When functions are activated, they will remain active even when other engines are called from the Control unit, but, if they are called up again, the function will turn off and will have to be reset .

When using the Control 80f, Central Control-i and Control Unit the Function Off button acts as a momentary switch and will activate the function only as long as the button is being depressed. When released, the function will cease. This is the best way to activate TELEX couplers, because this way they would not accidentally be left on and burn up.

C80 Decoder
This decoder is designed for 2-rail or 3-rail operation of AC motors. It is located in the locomotive and replaces the reversing unit in Märklin locos. Digital signals from the Central Unit are sent through the track system to the engine where it is picked up and analyzed to determine the address destination.

Decoders come with a color diagram showing the appropriate colors of the decoder wires and where they are connected to the various inputs and outputs.

C81 Decoder
The c81 decoder was designed to operate DC motors from Märklin's Digital Control Units. Their connection inside the loco is similar to the c80 decoder.

c80 and c81 Addresses
Each c80 and c81 decoder has a bank of 8 switches where the address is set between 01 and 80. A chart is included with the instruction booklets in digital locos which shows the switch settings for all the available addresses. It often indicates that address 68 is a reserved address, but it can be accessed by turning on switches 4 and 6. The digital code is acted upon if the address being sent by the Central Unit agrees with the switch setting of the decoder.