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Turnout Decoder N Scale #4

With the two decoders N4L and N4R the KATO UNITRACK N-gauge turnouts #4 radius 481 mm can be digitized. The decoders replace the original circuit board and are fully integrated into the turnout. Power is supplied via the tracks. The decoders can be controlled by any digital command station that can switch turnouts in DCC protocol.

Proto Design Labs N4L for KATO UNITRACK N gauge turnout #4 radius 481 mm with branch to the left. The turnout has KATO item number 20-220 or NOCH item number 7078203.

Proto Design Labs N4R for the KATO UNITRACK N-gauge turnout #4 radius 481 mm with branch to the right. The turnout has KATO item number 20-221 or NOCH item number 7078204.

Screwed mounting in the track bed with only two solder connections

The decoder is screwed into the track bed with the original nuts and screws and the two strands of the coil are soldered to the decoder.

By removing the original circuit board, there can be no problems due to incorrectly set configuration screws for frog voltage and power routing depending on the turnout position. Please also note, older turnouts are incorrectly labeled on the back with regard to power routing.

Design avoids short circuits

The #4 turnouts offer the option to supply the frog of the turnout with polarized current. Turning this option on and off is done by the position of the screw labeled "Frog Power". When frog polarization is switched on, a turnout must not be driven against its position, as this will inevitably lead to a short circuit. To cancel the short circuit, the turnout would have to be switched manually since the main track is without voltage due to the short circuit and thus the turnout cannot be switched by the digital command station. A serious problem if the turnout is not accessible, e.g. in a tunnel or staging yard.

After installation of the N4 decoder the frog is always without power. The turnout can be driven (cut open) against the switching direction without danger of a short circuit.

No wiring necessary

The decoders draw their power directly from the main track. No wiring of any kind is necessary. Modern model railroad command stations allow to switch several turnouts individually and with a slight time delay to reduce the maximum power consumption.

Quick and easy layout setup - Perfect for fixed and temporary layouts

Since no additional wiring is required, layouts are quick and easy to set up. Whether permanently mounted or as a "carpet track" for temporary operation.

NMRA tested

Die National Model Railroad Association, der Nationale Verband der Modellbahner in den USA, reglementiert und normt die Modellbahnen in den USA. Die Decoder von Proto Design Labs wurden von der NMRA ausführlich getestet.

Easy setting of the turnout address

Setting the turnout address is as simple as connecting the two pins of the decoder and sending a switching command to the address to be programmed.

Programming on main track (POM)

Proto Design Labs' N4 decoders can be programmed on the main track as so-called simple accessory decoders. The turnout address can be set, the switching direction can be reversed, and the switching duration can be adjusted.

DC compatible

A layout equipped with decoders from Proto Design Labs can also be operated with direct current (DC) without any problems. The decoders are designed for this and will not be damaged.

The two pins are only used for address programming. No switch lever can be connected to them for switching via DC. If this should happen accidentally, it will of course not damage the decoder.

RailCom® compatible

Of course, unlike competitive products, the decoders also work in conjunction with RailCom, a standard that allows decoders to send feedback to the digital command station or to special receiver modules. The decoders themselves do not send feedback via RailCom.



Fitting Instructions

Continue to installation instructions...


Set turnout address

Attach jumper to the two pins.

Connect the turnout to the main track output of the command station and switch on the power.

When the jumper is plugged in, a green LED on the turnout decoder lights up. This is also visible through the track bed.

Send switching command for the desired address. The turnout switches immediately.

Remove jumper and test programming.

The decoder can be programmed to addresses 1 to 2044. The default address is 1.

Please note when using products from several manufacturers: Not all digital command stations address so-called simple accessory decoders identically, often for reasons of compatibility with older products. This leads to the fact that addresses are not identical over the whole address range or that an offset is necessary. For the products of an Austrian manufacturer the option "DCC turnout-addressing according RCN-213" should be switched on, unless compatibility with older products is necessary. If the option is deactivated, an offset of 4 is necessary for most addresses. I.e. if the turnout decoder was programmed to the value 10 with a digital command station of another manufacturer, the address 14 must be used for control. For addresses 1 to 3 an offset of 1 is necessary and 2045=1, 2046=5, 2047=6, 2048=7.

Tip: Alternatively, the two pins can also be connected to each other, e.g. with current-conducting tweezers or a screwdriver, while the switching command is being sent.


DCC Configuration Variables

The turnout decoder can be programmed on the main track as a simple accessory decoder. This kind of programming is called POM (Program on Main). A change of the preset values is usually not necessary. Setting the turnout address is faster via the two pins. However, POM allows to change the address of a turnout even in a fixed layout without access to the pins. Please note that many digital command stations do not yet support POM for simple accessory decoders and with linear addressing 1 - 2044.

CV 1 / CV 9: Turnout address LSB / MSB

The address of the turnout results from the value of CV 1 added by CV 9 multiplied by 256. Example: CV 1 = 17, CV 9 = 3: 17 + 3 * 256 = 785. When programming note that after setting the first CV the decoder address already changes. The change of the second CV must then be done with this intermediate address. Before programming the first CV, make sure that the intermediate address is not already used by another decoder. If necessary, start with the other CV first. For assistance an Excel file is available: Download.

Default 1 / 0

CV 3: Switching time

Set the time period in milliseconds from 0 to 255, in which the coil is supplied with current. In delivery state set to the optimal value of 50 milliseconds.

Default 50

CV 4: Reverse switching direction

With CV 4 = 255 the switching direction is reversed. Can be used if the digital command station sends non-standard switching commands or if the coil was soldered with the wrong polarity.

Default 0

CV 33: Address mapping Digitrax®

Special optional address translation.

Default 0


Compatibility test RailCom®: Digitrax® DS51K1 vs. Proto Design Labs N4

There are some forum posts claiming that the Digitrax® DS51K1 DCC turnout decoder for KATO turnouts does not work when using RailCom®. RailCom is a standard widely used with European products, which allows decoders to send feedback to the digital command station or to special receiver modules. This can be used, for example, to automatically detect locomotives placed on the tracks or to implement track occupancy detection.

I test out how this looks with compatibility and also see if the N4L decoder from Proto Design Labs has problems with RailCom. As expected, the test confirms the statements. As soon as RailCom is switched on in the digital command station, which is often the case by default, the DS51K1 no longer responds to switching commands. It is completely irrelevant whether there is a RailCom-capable decoder in use at all. The pauses in the DCC data stream sent by the command station are sufficient to paralyze the decoder, it then no longer responds to switch commands. Of course, the decoders from Proto Design Labs also work with RailCom.

Please note: The decoders from Proto Design Labs do not send feedback about the position of the turnout via RailCom.


Tip: Programming access

If you want to change the address of a turnout decoder in a fixed layout, but use a digital command station that does not support POM for simple accessory decoders, you have to connect the two pins of the decoder to program the new turnout address. To do this, you could either drill a hole of e.g. 10 mm in the base plate at the appropriate point when setting up the layout or simply drill a small hole with a diameter of 1 mm in the track bed before mounting it in the layout. Alternatively, you could also attach or solder a short cable to the pins. Of course, it is even better to assign the addresses right away so that no changes are necessary later.


Detailed information can also be found on the manufacturer's website: www.protodesignlabs.com

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