{"title":"Detectors — Railroad","description":"\u003cp\u003eModel railroad detectors and occupancy sensors are essential for automated signaling, block detection, and layout control. This category covers the full range of detection solutions for DCC and DC layouts — from block occupancy to grade crossing automation. Explore related categories: \u003ca href=\"\/collections\/controllers-railroad\"\u003e\u003cstrong\u003e\u003cu\u003eDCC Controllers\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e and \u003ca href=\"\/collections\/connectors-blocks\"\u003e\u003cstrong\u003e\u003cu\u003eWiring Components\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e. Supported by \u003ca href=\"http:\/\/www.circuitron.com\/\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e, \u003ca href=\"https:\/\/www.digitrax.com\/\"\u003e\u003cstrong\u003e\u003cu\u003eDigitrax\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e, and \u003ca href=\"https:\/\/www.ncedcc.com\/\"\u003e\u003cstrong\u003e\u003cu\u003eNCE\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e","products":[{"product_id":"800-5202-dt-2-grade-crossing-detector","title":"800-5202 DT-2 Grade Crossing Detector","description":"\u003cp\u003eThe Circuitron DT-2 is a fully assembled grade crossing detector for DC model railroad layouts. It uses four Opto-Sensors and bidirectional detection to reproduce realistic crossing activation for short or long trains.\u003c\/p\u003e\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Fully assembled electronic circuit on a 3 x 3 inch printed circuit board.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eScale:\u003c\/strong\u003e Not specified; designed for model railroad layouts rather than a single scale.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e Operates from any 10–18 volt AC or DC power source and controls DC-powered loads up to 250 mA.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eContents:\u003c\/strong\u003e One DT-2 detector circuit board and four Opto-Sensors for a normal installation.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDetection:\u003c\/strong\u003e Bidirectional operation with circuit memory that keeps the crossing output on until the last car clears.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImportant detail:\u003c\/strong\u003e On layouts using Command Control, train-direction sensing is defeated and a manual panel switch is required to establish direction before a train reaches the crossing.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eFor Model Railroad Layouts\u003c\/h2\u003e\n\u003cp\u003eThe DT-2 detects a train that stops short of the crossing and backs away, then turns the output off. It is suited to modelers building more realistic grade crossing signals and control systems.\u003c\/p\u003e\n\u003cp\u003eLearn more from the \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics website\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e or browse \u003ca href=\"https:\/\/mpmhobbies.com\/collections\/train-layout-construction\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eTrain Layout Construction\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e products for related layout projects.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46404119298279,"sku":"TOR5202IH","price":43.67,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/products\/800-5202-dt-2-grade-crossing-detector-mpm-hobbies.jpg?v=1788154434"},{"product_id":"800-5521-bd-1hd-block-occupancy-detector-opto-electronic","title":"800-5521 BD-1HD Block Occupancy Detector- Opto-Electronic","description":"\u003cp\u003eThe Circuitron BD-1HD Block Occupancy Detector is an electronic module for model railroaders building bi-directional train traffic blocks. It provides positive occupied and clear indications and supports two-color signals at both ends of a block without additional drivers.\u003c\/p\u003e\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Circuitron Electronics\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct:\u003c\/strong\u003e BD-1HD block occupancy detector, opto-electronic\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Bi-directional model railroad block detection\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSignal support:\u003c\/strong\u003e Two-color signals at each end of a block\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutput:\u003c\/strong\u003e Heavy-duty output transistors for lamps in large-scale signals, with up to 500 mA per output\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eScale:\u003c\/strong\u003e Not specified by the manufacturer\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSet size:\u003c\/strong\u003e One detector product\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eHow It Works\u003c\/h2\u003e\n\u003cp\u003eThe system provides an occupied indication whenever any piece of rolling stock is within the block and a clear indication when no train is detected. The BD-1HD is based on the BD-1 design and adds heavy-duty output transistors for higher-power signal applications.\u003c\/p\u003e\n\u003ch2\u003eManufacturer Information\u003c\/h2\u003e\n\u003cp\u003eFor manufacturer details, visit \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e. For related layout components, browse \u003ca href=\"https:\/\/mpmhobbies.com\/collections\/train-layout-construction\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eTrain Layout Construction\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46688016728295,"sku":"TOR5521IH","price":29.6,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/products\/800-5521-bd-1hd-block-occupancy-detector-opto-electronic-mpm-hobbies.jpg?v=1788135805"},{"product_id":"800-5250-df-1-grade-crossing-detector-with-flasher","title":"800-5250 DF-1 Grade Crossing Detector with Flasher","description":"\u003cp\u003eThe Circuitron DF-1 is a single-direction grade crossing detector and alternating flasher for model railroaders building layouts in any scale. It detects a locomotive or train without modifications to rolling stock and operates independently of track power.\u003c\/p\u003e\n\u003ch2\u003eDF-1 Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct:\u003c\/strong\u003e Grade crossing detection circuit with alternating flasher on one printed circuit board\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eScale:\u003c\/strong\u003e Compatible with any model railroad scale\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e AC, DC, and command control systems (DCC)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDetection:\u003c\/strong\u003e Single-direction operation for a single locomotive or a train of up to 100 cars\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower:\u003c\/strong\u003e Requires a 10–18-volt AC or DC power source and remains independent of track power\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBoard size:\u003c\/strong\u003e 3 × 3 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlasher capacity:\u003c\/strong\u003e Two 250 milliamp loads, approximately four grain-of-wheat lamps or 10 LEDs per side\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSet contents:\u003c\/strong\u003e One DF-1 circuit board\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eLayout Integration\u003c\/h2\u003e\n\u003cp\u003eThe Accessory OUT terminal provides a ground output whenever a train is detected. It can be used with additional circuitry to control crossing bells, gates, or other layout accessories. Other Circuitron detection circuits, including the DT-1, DT-2, and DT-3, can connect to the flasher section when parallel-track detection is needed.\u003c\/p\u003e\n\u003ch2\u003eMore Information\u003c\/h2\u003e\n\u003cp\u003eSee the \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics product information\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e and browse \u003ca href=\"https:\/\/mpmhobbies.com\/collections\/464452255975\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eTrain Layout Construction supplies\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e for related layout projects.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46688112935143,"sku":"TOR5250IH","price":40.71,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/products\/800-5250-df-1-grade-crossing-detector-with-flasher-mpm-hobbies.jpg?v=1788135808"},{"product_id":"800-5203-dt-3-grade-crossing-detection-circuit-single-direction","title":"800-5203 DT-3 Grade Crossing Detection Circuit- Single Direction","description":"\u003cp\u003eThe CIRCUITRON DT-3 is a single-direction grade crossing detection circuit for model railroad layouts. It detects train movement without modifications to rolling stock and works with AC, DC, or DCC track power.\u003c\/p\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Electronic circuit assembled on a printed circuit board.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize:\u003c\/strong\u003e 2 × 3 inch printed circuit board.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eScale:\u003c\/strong\u003e Suitable for any model railroad scale.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower:\u003c\/strong\u003e 10–18 volt AC or DC supply.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eContents:\u003c\/strong\u003e DT-3 single-direction grade crossing detection circuit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDetection:\u003c\/strong\u003e Supports accurate grade crossing action for a single locomotive or a 100-car train.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eCompatibility\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eCompatible with AC or DC track power and command control systems (DCC).\u003c\/li\u003e\n\u003cli\u003eNo rolling stock modifications are required.\u003c\/li\u003e\n\u003cli\u003eControls a CIRCUITRON Alternating Flasher, Bell Ringer Circuit, or external relay.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eLayout Applications\u003c\/h2\u003e\n\u003cp\u003eUse the DT-3 in model railroad layouts alongside \u003ca href=\"https:\/\/mpmhobbies.com\/collections\/train-layout-construction\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eTrain Layout Construction\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e supplies and projects.\u003c\/p\u003e\n\u003ch2\u003eManufacturer\u003c\/h2\u003e\n\u003cp\u003eLearn more about model railroad electronics from \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46688915587303,"sku":"TOR5203IH","price":25.91,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/files\/800-5203-dt-3-grade-crossing-detection-circuit-single-direction-mpm-hobbies.jpg?v=1788135812"},{"product_id":"800-5201-dt-1-grade-crossing-detector","title":"800-5201 DT-1 Grade Crossing Detector","description":"\u003cp\u003eThe Circuitron 800-5201 DT-1 Grade Crossing Detector is a bi-directional detection circuit for DC model train layouts. It provides an output when rolling stock covers either Opto-Sensor, without modifying the rolling stock.\u003c\/p\u003e\u003ch2\u003eProduct Details\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBrand and model:\u003c\/strong\u003e Circuitron DT-1, item 800-5201\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUse:\u003c\/strong\u003e Grade crossing detection on layouts using DC track power\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDetection:\u003c\/strong\u003e Bi-directional Opto-Sensor operation provides an output when either sensor is covered by rolling stock\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e DC model train layouts; no rolling stock modifications are required\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Electronic detection circuit; the available product information does not specify a material\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eScale:\u003c\/strong\u003e Not specified in the available product information\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePackage contents:\u003c\/strong\u003e Not specified in the available product information\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eMore Information\u003c\/h2\u003e\u003cp\u003eFor manufacturer information, visit \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e. Browse \u003ca href=\"https:\/\/mpmhobbies.com\/collections\/464452255975\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eTrain Layout Construction products\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e for complementary layout supplies.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46688947634407,"sku":"TOR5201IH","price":29.63,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/files\/800-5201-dt-1-grade-crossing-detector-mpm-hobbies.png?v=1788135813"},{"product_id":"800-5501-bd-1-block-occupancy-detector-opto-electronic","title":"800-5501 BD-1 Block Occupancy Detector- Opto-Electronic","description":"\u003cp\u003eThe Circuitron BD-1 is a bidirectional block occupancy detector for model railroad layouts. It uses opto-electronic sensors to indicate when rolling stock occupies a protected block section.\u003c\/p\u003e\n\u003ch2\u003eFeatures and compatibility\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Detects rolling stock in a block section and supports reversing movement.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSensor system:\u003c\/strong\u003e Two pairs of opto-sensors are included and mount between the ties at the block endpoints.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSignal output:\u003c\/strong\u003e Driver circuitry powers a pair of two-color LED or incandescent block signals at each end. LED signals require common-anode wiring.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower:\u003c\/strong\u003e Requires filtered 10–18V DC input and provides outputs up to 250 mA.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Printed circuit board with opto-electronic sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eScale:\u003c\/strong\u003e Not applicable; this is an electronic model railroad layout accessory.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBoard size:\u003c\/strong\u003e 2 x 3 inches.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWhat's included\u003c\/h2\u003e\n\u003cp\u003eOne BD-1 circuit board and two pairs of opto-sensors. The unit is intended for model railroad layout installation, and no rolling-stock modifications are necessary.\u003c\/p\u003e\n\u003ch2\u003eManufacturer information\u003c\/h2\u003e\n\u003cp\u003eFor product specifications and manufacturer information, visit \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46689249788135,"sku":"TOR5501IH","price":29.6,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/files\/800-5501-bd-1-block-occupancy-detector-opto-electronic-mpm-hobbies.gif?v=1788135825"},{"product_id":"800-5522-bd-2hd-block-occupancy-detector-current-sensing","title":"800-5522 BD-2HD Block Occupancy Detector- Current Sensing","description":"\u003cp\u003eThe Circuitron BD-2HD is a current-sensing block occupancy detector for model railroad layouts. Its brief turn-off delay helps reduce missed detection from dirty wheels, while the outputs can drive common two-color block signals.\u003c\/p\u003e\n\u003ch2\u003eBD-2HD features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct type:\u003c\/strong\u003e Current-sensing block occupancy detector for model railroad layouts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBoard:\u003c\/strong\u003e 2-inch by 3-inch printed circuit board\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e LED-type or incandescent 2-color block signals, Circuitron PCMT (Printed Circuit Mounting Track), and large-scale equipment\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTrack power:\u003c\/strong\u003e Standard 6-amp track power capacity\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDetection:\u003c\/strong\u003e Approximately 1\/2-second turn-off delay\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutput:\u003c\/strong\u003e Maximum current capacity of 250 mA, with signal-driving capacity increased to 500 mA per output\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eContents:\u003c\/strong\u003e One BD-2HD circuit board; a set quantity is not specified in the current product details\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eInstallation notes\u003c\/h2\u003e\n\u003cp\u003eThe board supports daisy-chain wiring for multiple blocks and is designed to snap into a section of Circuitron PCMT for installation in a model railroad layout.\u003c\/p\u003e\n\u003ch2\u003eProduct details\u003c\/h2\u003e\n\u003cp\u003eThis is an electronic layout accessory, not a model kit, and no scale is specified in the current product details.\u003c\/p\u003e\n\u003cp\u003eLearn more from \u003ca href=\"http:\/\/www.circuitron.com\/\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eCircuitron Electronics\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e and explore related \u003ca href=\"https:\/\/mpmhobbies.com\/collections\/train-layout-construction\" target=\"_self\"\u003e\u003cstrong\u003e\u003cu\u003eTrain Layout Construction supplies\u003c\/u\u003e\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e","brand":"Circuitron Electronics","offers":[{"title":"Default Title","offer_id":46693033017575,"sku":"TOR5522IH","price":28.86,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/files\/800-5522-bd-2hd-block-occupancy-detector-current-sensing-mpm-hobbies.jpg?v=1788135829"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0636\/7798\/9095\/collections\/optimized_collection_464451928295.jpg?v=1787883383","url":"https:\/\/mpmhobbies.com\/collections\/detectors-railroad.oembed","provider":"MPM Hobbies","version":"1.0","type":"link"}