DCC Block Detector



Isolated, reliable, easy-to-install, single-channel DCC block detector.  Compatible with a wide variety of other block detectors on the market, the CKT-BD1 provides two open collector outputs (one for detection, one for no detection) with optional pull-up resistors and adjustable sensitivity.  Based on a current transformer, the detector maintains isolation between your track and signal systems.

For our friends invested in C/MRI, we offer an optional connector that replaces the screw terminals with a plug that connects directly into Dr. Chubb's detector motherboard (ODMB) and provides full compatibility with the DCCOD.


  • Isolated, current-transformer based
  • Highly sensitive (12-15k ohms)
  • Simple sensitivity adjustment
  • Two opposite polarity, open-collector outputs (40V / 250mA capable)
  • Optional onboard output pull-up resistors
  • Powered from 5V to 18V
  • Optional C/MRI DCCOD-compatible connector – plugs into C/MRI detector motherboards!


1.8"(L) x 1.5"(W) x 0.875"(H)


The complete gEDA design files are available on GitHub.

User Manual


  • $16.00

Available Options

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News & Application Notes

Introducing the CKT-BD1 DCC Block Detector

I’d like to introduce you to ISE’s latest model railroad product – the CKT-BD1 single channel DCC block detector!

The CKT-BD1 – our brand new single channel DCC block detector

This little DCC current-based detector is designed to be highly sensitive while being resistant to false triggering, robust, and very easy to install.  All you need to do is pass one of the bus wires to the block to be detected through the current transformer and provide 5-18VDC to power up the detector.   It can run on as little as 5VDC at 15mA, so it’s perfect for connecting to digital logic such as Arduinos or C/MRI systems.   It has open drain outputs for both detecting and not detecting states, so it’s compatible with a wide range of other model railroad products such as the Modular Signaling System, C/MRI, input modules for systems like JMRI, standalone signal sytems, or even just seeing if there’s something in that hidden section of track on your layout.  It also has adjustable sensitivity, so you can tune it to ignore leakage current through your trackwork while still picking up minute currents from rolling stock.  Precision current measurement circuitry and a little digital microcontroller onboard helps filter the response so that you achieve maximum sensitivity without false triggers.


Block Detectors – An Epic Tale

The development of ISE’s block detectors has been a fairly long adventure, so much so that the long, drawn-out development cycle through six or seven iterations has become a bit of a running joke between Michael and myself.  It’s served as a bit of a high water mark in terms of design revisions and major overhauls, and every time Michael and I have to rev something, there’s usually a comment of, “well, at least it’s not the !@#$ block detectors again…”

With today’s introduction of the CKT-BD1, I thought it might be interesting to let you all in on how this evolved, and how we arrived where we are today – a rock solid design that I believe in as much as our bulletproof IR sensors.   It’s the sort of thing that no sane manufacturer would do – sort of like running the corporate dirty laundry up the flagpole and waving it around.  But then again, we’re a different sort of electronics company, and Michael’s been arguing for years that I’m not quite sane…



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