Coil Accessory Decoders


When we speak of coil switch machines, by far and away we are talking about TWIN COIL switch machines. Twin coil machines are current based devices. The amount of current they need will depends on the given turnouts loading effect which refers to over coming both stiction and friction The larger the load, the more energy it takes to move the point rails from one position to the other. However, there are limits to the amount of current a given twin coil machine can support before it get overloaded. Hence there are needs for different sizes of twin coil machines. Some target for N scale and some for G scale.


You must first know what type of Twin Coil switch machine you have to know get an idea of the current they will need to allow them to operate properly. This becomes even more important if you intend to operate more than one twin coil switch machine at the same time as in setting up crossover between two tracks.

To find the load level of you Twin Coil switch machine needs, go here first: Coil Switch Machines


Small twin coils machines are designed to drive very small scale turnouts. Many are specific designed to drive a specific turnout of a specific scale. Hence the mechanical load on the coil is very well defined and the coil is sized to handle that specific load with maximum efficiency.

Big twin coil switch machines are more generic in that they can be adapted to work with almost any scale turnout/track switch. Since they can be used with large scale track switches, the mechanical load can be high and as such the coil will need to bigger and consume more current to drive this large load. Many of the generic switch machines also offer additional contacts that can be used to do power routing, panel indicators or simple signaling.


Some coil compatible DCC accessory decoders include what is called a Capacitive Discharge (CD) power supply onboard. This option greatly simplifies both the input power supply requirements (reduces them) and/or allows one to drive high loads. Higher loads can be a larger switch machine or multiple small switch machines in parallel. The down side of these power supplies is that they can take some time to recharge between switch machine events such that back to back throwing of switches is not possible without one waiting a second or two. To learn more about capacitive discharge go here:

Below is a table of DCC Accessory Decoder and their current delivery capabilities.


The key information is the "Power Class" which is divided into two categories. Low and High. This will tell you what are the compatible twin coil switch machines it will work with. To find out more about the switch machine load requirements, go here: Coil Switch Machines