{"id":1131,"date":"2026-10-25T18:53:15","date_gmt":"2026-10-25T17:53:15","guid":{"rendered":"https:\/\/www.jtdigital.de\/?p=1131"},"modified":"2026-10-25T22:42:48","modified_gmt":"2026-10-25T21:42:48","slug":"plux22-21mtc-schnittstelle-belegung","status":"publish","type":"post","link":"https:\/\/www.jtdigital.de\/en\/plux22-21mtc-schnittstelle-belegung\/","title":{"rendered":"PluX22 and 21MTC: decoder interfaces and pin assignment explained"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Anyone digitalising a locomotive almost always comes across two terms: <strong>PluX22<\/strong> and <strong>21MTC<\/strong>. Both are standardised decoder interfaces \u2013 the decoder is simply plugged in instead of soldered. Here we explain how the two differ, how the contacts are assigned and what to look out for during installation.<\/p>\n\n\n\n<div class=\"wp-block-group jt-tldr is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"jt-box-title wp-block-paragraph\"><strong>Key points at a glance<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Both interfaces have 22 contacts at a 1.27 mm pitch; pin 11 is missing as reverse-polarity protection.<\/li>\n\n<li>PluX22: all function outputs are amplified \u2013 lamps and LEDs (with a series resistor) can be connected directly.<\/li>\n\n<li>21MTC: AUX3 to AUX6 supply logic level only; in return, the interface is also suitable for AC motors.<\/li>\n\n<li>If there is no interface in the loco, an adapter board helps \u2013 solder it in once, then just plug in the decoder.<\/li>\n<\/ul>\n<\/div>\n\n\n\n<div class=\"wp-block-group jt-toc is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"jt-box-title wp-block-paragraph\"><strong>Contents<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><a href=\"#was-ist-eine-decoderschnittstelle\">What is a decoder interface?<\/a><\/li>\n\n<li><a href=\"#vergleich\">PluX22 and 21MTC compared<\/a><\/li>\n\n<li><a href=\"#belegung\">Contact assignment<\/a><\/li>\n\n<li><a href=\"#einbau\">What to look out for during installation<\/a><\/li>\n\n<li><a href=\"#nachruesten\">Retrofitting with an adapter board<\/a><\/li>\n\n<li><a href=\"#faq\">Frequently asked questions<\/a><\/li>\n<\/ol>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"was-ist-eine-decoderschnittstelle\">What is a decoder interface?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A decoder interface is a standardised socket on the circuit board in the vehicle. Track, motor, lights, speaker and other functions are always on the same contacts. This means any decoder with the same interface fits \u2013 regardless of manufacturer \u2013 and can later be swapped without a soldering iron. PluX is defined in the <strong>NEM 658<\/strong> and 21MTC in the <strong>NEM 660<\/strong> of the European model railway association MOROP; the detailed technical specifications can be found in the RailCommunity standards RCN-122 and RCN-121.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"vergleich\">PluX22 and 21MTC compared<\/h2>\n\n\n\n<div class=\"wp-block-columns jt-cards is-layout-flex wp-container-core-columns-is-layout-3a88641f wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<p class=\"jt-card-top wp-block-paragraph\">PluX22 \u00b7 NEM 658<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Decoder has the <strong>pins<\/strong>, the vehicle has the socket<\/li>\n\n<li>Front\/rear lights and AUX1\u20137, <strong>all amplified<\/strong><\/li>\n\n<li>for DC motors (including coreless motors)<\/li>\n\n<li>Decoder max. 30 (35) \u00d7 16 \u00d7 6 mm<\/li>\n<\/ul>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<p class=\"jt-card-top jt-card-dark wp-block-paragraph\">21MTC \u00b7 NEM 660<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Decoder has the <strong>socket<\/strong>, the vehicle has the pins<\/li>\n\n<li>AUX1\u20132 amplified, <strong>AUX3\u20136 logic level only<\/strong><\/li>\n\n<li>for DC, coreless and AC motors<\/li>\n\n<li>Decoder max. 30 \u00d7 15.5 \u00d7 6.5 mm<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">The most important practical consequence: with <strong>PluX22<\/strong> you can connect lamps or LEDs (with a series resistor) directly to all outputs. With <strong>21MTC<\/strong> AUX3 to AUX6 supply only a logic signal of at most 0.5 mA; the vehicle needs an amplifier circuit on its own board for this, or you choose a decoder with amplified outputs.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"belegung\">Contact assignment<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Select the interface to see the assignment of all contacts:<\/p>\n\n\n\n<div class=\"jt-tabs\">\n<span id=\"belegung-plux22\" class=\"jt-anchor\"><\/span><span id=\"belegung-21mtc\" class=\"jt-anchor\"><\/span>\n<div class=\"jt-tabbar\" role=\"tablist\"><a href=\"#belegung-plux22\" class=\"jt-tab t-plux\">PluX22<\/a><a href=\"#belegung-21mtc\" class=\"jt-tab t-mtc\">21MTC<\/a><\/div>\n<div class=\"jt-panel p-plux\">\n<h3>PluX22 pin assignment according to NEM 658<\/h3>\n<div class=\"jt-pins-wrap\"><div class=\"jt-pins\"><span class=\"jt-pin c-g\"><b>1<\/b><small>GPIO_C<\/small><\/span><span class=\"jt-pin c-g\"><b>3<\/b><small>ZBCLK<\/small><\/span><span class=\"jt-pin c-p\"><b>5<\/b><small>GND<\/small><\/span><span class=\"jt-pin c-l\"><b>7<\/b><small>F0_f<\/small><\/span><span class=\"jt-pin c-p\"><b>9<\/b><small>U+<\/small><\/span><span class=\"jt-pin c-i\"><b>11<\/b><small>Index<\/small><\/span><span class=\"jt-pin c-l\"><b>13<\/b><small>F0_r<\/small><\/span><span class=\"jt-pin c-x\"><b>15<\/b><small>LS_A<\/small><\/span><span class=\"jt-pin c-x\"><b>17<\/b><small>LS_B<\/small><\/span><span class=\"jt-pin c-a\"><b>19<\/b><small>AUX4<\/small><\/span><span class=\"jt-pin c-a\"><b>21<\/b><small>AUX6<\/small><\/span><span class=\"jt-pin c-a\"><b>2<\/b><small>AUX3<\/small><\/span><span class=\"jt-pin c-g\"><b>4<\/b><small>ZBDATA<\/small><\/span><span class=\"jt-pin c-p\"><b>6<\/b><small>Cap+<\/small><\/span><span class=\"jt-pin c-m\"><b>8<\/b><small>Motor +<\/small><\/span><span class=\"jt-pin c-m\"><b>10<\/b><small>Motor \u2212<\/small><\/span><span class=\"jt-pin c-s\"><b>12<\/b><small>Rail R<\/small><\/span><span class=\"jt-pin c-s\"><b>14<\/b><small>Rail L<\/small><\/span><span class=\"jt-pin c-a\"><b>16<\/b><small>AUX1<\/small><\/span><span class=\"jt-pin c-a\"><b>18<\/b><small>AUX2<\/small><\/span><span class=\"jt-pin c-a\"><b>20<\/b><small>AUX5<\/small><\/span><span class=\"jt-pin c-a\"><b>22<\/b><small>AUX7<\/small><\/span><\/div><\/div>\n<p class=\"jt-legend\"><span><i class=\"c-s\"><\/i>Track<\/span><span><i class=\"c-m\"><\/i>Motor<\/span><span><i class=\"c-l\"><\/i>Lights<\/span><span><i class=\"c-a\"><\/i>Output, amplified<\/span><span><i class=\"c-g\"><\/i>Logic level \/ train bus<\/span><span><i class=\"c-x\"><\/i>Speaker<\/span><span><i class=\"c-p\"><\/i>Power supply<\/span><span><i class=\"c-i\"><\/i>Index<\/span><\/p>\n<p class=\"jt-pins-note\">Schematic arrangement of the 22 contacts in two rows; pin 11 is missing as reverse-polarity protection. PluX16 uses contacts 3 to 18.<\/p>\n<figure class=\"wp-block-image size-large jt-panel-img\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"490\" src=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-1024x490.jpg\" alt=\"Adapterplatine PluX22-Decoder neben einem Lokdecoder\" class=\"wp-image-216\" srcset=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-1024x490.jpg 1024w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-300x143.jpg 300w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-768x367.jpg 768w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-1536x734.jpg 1536w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-2048x979.jpg 2048w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-600x287.jpg 600w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-800x383.jpg 800w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Our <a href=\"\/en\/product\/adapterplatine-plux-22-decoder\/\">PluX22 adapter board<\/a> with decoder<\/figcaption><\/figure>\n<figure class=\"wp-block-table jt-pin-table\"><table><thead><tr><th>Pin<\/th><th>Connection<\/th><th>Meaning<\/th><\/tr><\/thead><tbody><tr><td><span class=\"jt-dot c-g\"><\/span>1<\/td><td>GPIO_C<\/td><td>Input\/output with logic level, e.g. wheel sensor<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>2<\/td><td>AUX3<\/td><td>Output 3, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>3<\/td><td>ZBCLK \/ GPIO_A<\/td><td>Train bus clock or input\/output (logic level), e.g. servo<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>4<\/td><td>ZBDATA \/ GPIO_B<\/td><td>Train bus data or input\/output (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-p\"><\/span>5<\/td><td>GND<\/td><td>Decoder minus<\/td><\/tr><tr><td><span class=\"jt-dot c-p\"><\/span>6<\/td><td>Cap+<\/td><td>Plus for buffer capacitor<\/td><\/tr><tr><td><span class=\"jt-dot c-l\"><\/span>7<\/td><td>F0_f<\/td><td>Front lights (headlights, forward)<\/td><\/tr><tr><td><span class=\"jt-dot c-m\"><\/span>8<\/td><td>Motor +<\/td><td>Motor (amplified output on function decoders)<\/td><\/tr><tr><td><span class=\"jt-dot c-p\"><\/span>9<\/td><td>U+<\/td><td>Decoder plus (common plus of the functions)<\/td><\/tr><tr><td><span class=\"jt-dot c-m\"><\/span>10<\/td><td>Motor \u2212<\/td><td>Motor (amplified output on function decoders)<\/td><\/tr><tr><td><span class=\"jt-dot c-i\"><\/span>11<\/td><td>Index<\/td><td>not assigned \u2013 reverse-polarity protection<\/td><\/tr><tr><td><span class=\"jt-dot c-s\"><\/span>12<\/td><td>Right rail<\/td><td>Right-hand current pickup (3-rail: centre pickup)<\/td><\/tr><tr><td><span class=\"jt-dot c-l\"><\/span>13<\/td><td>F0_r<\/td><td>Rear lights (headlights, reverse)<\/td><\/tr><tr><td><span class=\"jt-dot c-s\"><\/span>14<\/td><td>Left rail<\/td><td>Left-hand current pickup (3-rail: wheels)<\/td><\/tr><tr><td><span class=\"jt-dot c-x\"><\/span>15<\/td><td>LS_A<\/td><td>Speaker A<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>16<\/td><td>AUX1<\/td><td>Output 1, amplified, e.g. tail light (reverse)<\/td><\/tr><tr><td><span class=\"jt-dot c-x\"><\/span>17<\/td><td>LS_B<\/td><td>Speaker B<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>18<\/td><td>AUX2<\/td><td>Output 2, amplified, e.g. tail light (forward)<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>19<\/td><td>AUX4<\/td><td>Output 4, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>20<\/td><td>AUX5<\/td><td>Output 5, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>21<\/td><td>AUX6<\/td><td>Output 6, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>22<\/td><td>AUX7<\/td><td>Output 7, amplified<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">PluX22 according to NEM 658, 2025 edition<\/figcaption><\/figure>\n<\/div>\n<div class=\"jt-panel p-mtc\">\n<h3>21MTC pin assignment according to NEM 660<\/h3>\n<div class=\"jt-pins-wrap\"><div class=\"jt-pins\"><span class=\"jt-pin c-g\"><b>1<\/b><small>GPIO_A<\/small><\/span><span class=\"jt-pin c-g\"><b>2<\/b><small>GPIO_B<\/small><\/span><span class=\"jt-pin c-g\"><b>3<\/b><small>AUX6<\/small><\/span><span class=\"jt-pin c-g\"><b>4<\/b><small>AUX4<\/small><\/span><span class=\"jt-pin c-g\"><b>5<\/b><small>ZBCLK<\/small><\/span><span class=\"jt-pin c-g\"><b>6<\/b><small>ZBDATA<\/small><\/span><span class=\"jt-pin c-l\"><b>7<\/b><small>F0_r<\/small><\/span><span class=\"jt-pin c-l\"><b>8<\/b><small>F0_f<\/small><\/span><span class=\"jt-pin c-x\"><b>9<\/b><small>LS_A<\/small><\/span><span class=\"jt-pin c-x\"><b>10<\/b><small>LS_B<\/small><\/span><span class=\"jt-pin c-i\"><b>11<\/b><small>Index<\/small><\/span><span class=\"jt-pin c-s\"><b>22<\/b><small>Rail R<\/small><\/span><span class=\"jt-pin c-s\"><b>21<\/b><small>Rail L<\/small><\/span><span class=\"jt-pin c-p\"><b>20<\/b><small>GND<\/small><\/span><span class=\"jt-pin c-m\"><b>19<\/b><small>Motor +<\/small><\/span><span class=\"jt-pin c-m\"><b>18<\/b><small>Motor \u2212<\/small><\/span><span class=\"jt-pin c-g\"><b>17<\/b><small>AUX5<\/small><\/span><span class=\"jt-pin c-p\"><b>16<\/b><small>U+<\/small><\/span><span class=\"jt-pin c-a\"><b>15<\/b><small>AUX1<\/small><\/span><span class=\"jt-pin c-a\"><b>14<\/b><small>AUX2<\/small><\/span><span class=\"jt-pin c-g\"><b>13<\/b><small>AUX3<\/small><\/span><span class=\"jt-pin c-p\"><b>12<\/b><small>Vcc<\/small><\/span><\/div><\/div>\n<p class=\"jt-legend\"><span><i class=\"c-s\"><\/i>Track<\/span><span><i class=\"c-m\"><\/i>Motor<\/span><span><i class=\"c-l\"><\/i>Lights<\/span><span><i class=\"c-a\"><\/i>Output, amplified<\/span><span><i class=\"c-g\"><\/i>Logic level \/ train bus<\/span><span><i class=\"c-x\"><\/i>Speaker<\/span><span><i class=\"c-p\"><\/i>Power supply<\/span><span><i class=\"c-i\"><\/i>Index<\/span><\/p>\n<p class=\"jt-pins-note\">Schematic arrangement of the 22 contacts in two rows; pin 11 is missing as reverse-polarity protection. In the rotated mounting position the assignment is mirrored.<\/p>\n<figure class=\"wp-block-image size-large jt-panel-img\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"427\" src=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-1024x427.jpg\" alt=\"Adapterplatine 21MTC-Decoder neben einem Lokdecoder, schr\u00e4ge Ansicht\" class=\"wp-image-212\" srcset=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-1024x427.jpg 1024w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-300x125.jpg 300w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-768x320.jpg 768w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-1536x641.jpg 1536w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-2048x854.jpg 2048w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-600x250.jpg 600w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-800x334.jpg 800w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Our <a href=\"\/en\/product\/adapterplatine-21mtc-decoder\/\">21MTC adapter board<\/a> with decoder<\/figcaption><\/figure>\n<figure class=\"wp-block-table jt-pin-table\"><table><thead><tr><th>Pin<\/th><th>Connection<\/th><th>Meaning<\/th><\/tr><\/thead><tbody><tr><td><span class=\"jt-dot c-g\"><\/span>1<\/td><td>GPIO_A \/ AUX7<\/td><td>Sensor input A or output 7 (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>2<\/td><td>GPIO_B \/ AUX8<\/td><td>Sensor input B or output 8 (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>3<\/td><td>AUX6<\/td><td>Output 6 (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>4<\/td><td>AUX4<\/td><td>Output 4 (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>5<\/td><td>ZBCLK \/ GPIO_C<\/td><td>Train bus clock or input\/output, e.g. servo<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>6<\/td><td>ZBDATA \/ GPIO_D<\/td><td>Train bus data or input\/output<\/td><\/tr><tr><td><span class=\"jt-dot c-l\"><\/span>7<\/td><td>F0_r<\/td><td>Rear lights, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-l\"><\/span>8<\/td><td>F0_f<\/td><td>Front lights, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-x\"><\/span>9<\/td><td>LS_A<\/td><td>Speaker A<\/td><\/tr><tr><td><span class=\"jt-dot c-x\"><\/span>10<\/td><td>LS_B<\/td><td>Speaker B<\/td><\/tr><tr><td><span class=\"jt-dot c-i\"><\/span>11<\/td><td>Index<\/td><td>not assigned \u2013 reverse-polarity protection<\/td><\/tr><tr><td><span class=\"jt-dot c-p\"><\/span>12<\/td><td>Vcc<\/td><td>Internal decoder voltage (optional)<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>13<\/td><td>AUX3<\/td><td>Output 3 (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>14<\/td><td>AUX2<\/td><td>Output 2, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-a\"><\/span>15<\/td><td>AUX1<\/td><td>Output 1, amplified<\/td><\/tr><tr><td><span class=\"jt-dot c-p\"><\/span>16<\/td><td>U+<\/td><td>Decoder plus, buffer capacitor connection<\/td><\/tr><tr><td><span class=\"jt-dot c-g\"><\/span>17<\/td><td>AUX5<\/td><td>Output 5 (logic level)<\/td><\/tr><tr><td><span class=\"jt-dot c-m\"><\/span>18<\/td><td>Motor \u2212<\/td><td>Motor (AC motor: field coil B)<\/td><\/tr><tr><td><span class=\"jt-dot c-m\"><\/span>19<\/td><td>Motor +<\/td><td>Motor (AC motor: field coil A)<\/td><\/tr><tr><td><span class=\"jt-dot c-p\"><\/span>20<\/td><td>GND<\/td><td>Decoder minus<\/td><\/tr><tr><td><span class=\"jt-dot c-s\"><\/span>21<\/td><td>Left rail<\/td><td>Left-hand current pickup (3-rail: wheels)<\/td><\/tr><tr><td><span class=\"jt-dot c-s\"><\/span>22<\/td><td>Right rail<\/td><td>Right-hand current pickup (3-rail: centre pickup)<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">21MTC according to NEM 660, 2025 edition<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"einbau\">What to look out for during installation<\/h2>\n\n\n\n<div class=\"wp-block-group jt-tip jt-warn is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Mind the index pin:<\/strong> The missing pin 11 must match the blocked hole. Never force the decoder on \u2013 if it is plugged in the wrong way round, it can be damaged.<\/p>\n<\/div>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>21MTC: compact or rotated?<\/strong> Usually the decoder sits with the socket facing up, and the pins pass through the decoder board. Some vehicles use the rotated mounting position \u2013 the assignment is then mirrored. If in doubt, consult the vehicle\u2019s manual.<\/li>\n\n<li><strong>3-rail vehicles:<\/strong> The centre pickup goes to \u201cRail R\u201d, the wheels to \u201cRail L\u201d.<\/li>\n\n<li><strong>LEDs need series resistors.<\/strong> The outputs switch to ground; the voltage comes from U+. We have suitable <a href=\"\/en\/product\/smd-widerstaende-0603\/\">0603 SMD Resistors<\/a> in the shop.<\/li>\n\n<li><strong>Buffer capacitor<\/strong> connect only to Cap+ (PluX) or U+ (21MTC) and according to the decoder\u2019s instructions.<\/li>\n\n<li><strong>Without a decoder,<\/strong> a vehicle with an interface will only run with a bridging plug that connects track and motor.<\/li>\n<\/ul>\n\n\n\n<div class=\"wp-block-group jt-tip is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Practical tip:<\/strong> After installation, cover the solder pads of an adapter board with insulating tape. This avoids short circuits with the loco body and protects the decoder.<\/p>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"nachruesten\">No interface in the loco? How to retrofit<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Older models often have no interface or only an old NEM 652 socket. An adapter board helps here: you solder the loco\u2019s wires to the labelled solder pads once, then simply plug the decoder on \u2013 and can swap it at any time later. You will find the installation instructions on the page <a href=\"\/en\/anleitungen\/\">Manuals<\/a>.<\/p>\n\n\n\n<div class=\"wp-block-columns jt-prodcards is-layout-flex wp-container-core-columns-is-layout-3a88641f wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-vertically-aligned-stretch is-layout-flow wp-block-column-is-layout-flow\">\n<div class=\"wp-block-group is-vertical is-content-justification-stretch is-layout-flex wp-container-core-group-is-layout-d8dce8eb wp-block-group-is-layout-flex\" style=\"min-height:100%\">\n<figure class=\"wp-block-image size-medium jt-prod-img\"><a href=\"\/en\/product\/adapterplatine-plux-22-decoder\/\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"143\" src=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-300x143.jpg\" alt=\"Adapterplatine PluX22-Decoder neben einem Lokdecoder\" class=\"wp-image-216\" style=\"aspect-ratio:2\/1;object-fit:contain;width:100%;height:180px\" srcset=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-300x143.jpg 300w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-1024x490.jpg 1024w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-768x367.jpg 768w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-1536x734.jpg 1536w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-2048x979.jpg 2048w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-600x287.jpg 600w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000141-800x383.jpg 800w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\"><a href=\"\/en\/product\/adapterplatine-plux-22-decoder\/\">PluX22 adapter board<\/a><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">17 \u00d7 16 mm, all 22 contacts as solder pads, decoder swappable at any time.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\" style=\"margin-top:auto\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"\/en\/product\/adapterplatine-plux-22-decoder\/\">View product<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-vertically-aligned-stretch is-layout-flow wp-block-column-is-layout-flow\">\n<div class=\"wp-block-group is-vertical is-content-justification-stretch is-layout-flex wp-container-core-group-is-layout-d8dce8eb wp-block-group-is-layout-flex\" style=\"min-height:100%\">\n<figure class=\"wp-block-image size-medium jt-prod-img\"><a href=\"\/en\/product\/adapterplatine-21mtc-decoder\/\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"125\" src=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-300x125.jpg\" alt=\"Adapterplatine 21MTC-Decoder neben einem Lokdecoder, schr\u00e4ge Ansicht\" class=\"wp-image-212\" style=\"aspect-ratio:2\/1;object-fit:contain;width:100%;height:180px\" srcset=\"https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-300x125.jpg 300w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-1024x427.jpg 1024w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-768x320.jpg 768w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-1536x641.jpg 1536w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-2048x854.jpg 2048w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-600x250.jpg 600w, https:\/\/www.jtdigital.de\/wp-content\/uploads\/2026\/03\/P1000138-800x334.jpg 800w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\"><a href=\"\/en\/product\/adapterplatine-21mtc-decoder\/\">21MTC adapter board<\/a><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">13 \u00d7 15 mm, all 21 contacts as solder pads, decoder swappable at any time.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\" style=\"margin-top:auto\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"\/en\/product\/adapterplatine-21mtc-decoder\/\">View product<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">For your own circuits, the <a href=\"\/en\/product\/plux22-buchse-lose\/\">PluX22 socket<\/a> and the <a href=\"\/en\/product\/21-mtc-stecker-lose\/\">21MTC plug<\/a> are also available individually.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"faq\">Frequently asked questions<\/h2>\n\n\n\n<details class=\"wp-block-details jt-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Does a PluX16 decoder fit in a PluX22 interface?<\/summary>\n<p class=\"wp-block-paragraph\">Yes, provided there is enough space. PluX16 uses the middle contacts 3 to 18; the additional outputs AUX4 to AUX7 are then not available.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details jt-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Can I plug a 21MTC decoder into a PluX interface?<\/summary>\n<p class=\"wp-block-paragraph\">No. The pin assignment and connectors are different: with 21MTC the decoder has the socket, with PluX the pins. However, a suitable adapter board lets you convert the loco to the interface you want.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details jt-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>What do \u201camplified output\u201d and \u201clogic level\u201d mean?<\/summary>\n<p class=\"wp-block-paragraph\">An amplified output switches lamps, LEDs or smoke generators directly. An output with logic level supplies only a control signal (max. 0.5 mA) \u2013 this needs an amplifier circuit in the vehicle.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details jt-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Which interface is better?<\/summary>\n<p class=\"wp-block-paragraph\">Neither is better in principle. What matters is what is installed in the vehicle. For retrofitting where there is no existing interface, PluX22 is often more practical because all outputs are amplified; 21MTC is also suitable for AC motors.<\/p>\n<\/details>\n\n\n\n<p class=\"jt-sources wp-block-paragraph\"><em>Sources: NEM 658 (PluX) and NEM 660 (21MTC), each 2025 edition, MOROP; RCN-121 and RCN-122, RailCommunity.<\/em><\/p>","protected":false},"excerpt":{"rendered":"<p>PluX22 or 21MTC? We explain the differences between the two decoder interfaces, show the assignment of all contacts according to NEM 658 and NEM 660, and give tips for installation.<\/p>","protected":false},"author":29,"featured_media":216,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"jt_en_seo_title":"PluX22 & 21MTC: Interface and Pin Assignment Explained | JT Digital","jt_en_seo_desc":"PluX22 or 21MTC? The differences, the assignment of all 22 contacts according to NEM 658\/660 and tips for installing decoders \u2013 clearly explained.","footnotes":""},"categories":[149,147],"tags":[],"class_list":["post-1131","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-digitalisierung","category-wissen-praxis"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/posts\/1131","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/users\/29"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/comments?post=1131"}],"version-history":[{"count":9,"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/posts\/1131\/revisions"}],"predecessor-version":[{"id":1146,"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/posts\/1131\/revisions\/1146"}],"wp:attachment":[{"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/media?parent=1131"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/categories?post=1131"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jtdigital.de\/en\/wp-json\/wp\/v2\/tags?post=1131"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}