• Interlocking-In-A-Box (IIAB)

Interlocking-In-A-Box (IIAB)



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This item is custom built to order.  Please contact us for details.

The Iowa Scaled Engineering Interlocking-In-A-Box (IIAB) provides the signal logic to control a fully automatic interlocking on a model railroad. It can be used to manage a crossing of two active main lines with signals on both, or more typically, it can be used to manage the crossing of an active (modeled) main line and an inactive (dummy) main line. Each main line can have one siding, on either side of the diamond, and the signals respond prototypically based on the position of the switch points.


  • Fully automatic interlocking with built-in signal logic (signals not included)
  • Ability to simulate trains schedules using an Iowa Scaled Engineering fast clock
  • Configurable time lock and timeout delays to suit any application
  • Supports one siding on each main line with corresponding signal indications
  • Interfaces with infrared or current-based block detectors
  • Optional automatic interchange can be triggered by simulated trains
  • Simple configuration with the MRGui utility


  • IIAB Module
  • One IR Sensor for the diamond
  • 12V, 1A Power Supply
  • 8 x 10kΩ Input Pull-Up Resistors (Color Code = brown black orange)
  • 16 x 330Ω LED Current-Limiting Resistors (Color Code = orange orange brown)
  • Programmer for use with the MRGui configuration utility (only one required/shipped per order - discount applied automatically)


The complete gEDA design files are available on GitHub.

User Manual


  • $99.00

  • 2 or more $94.00

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We will be at the St. Louis RPM Meet later in the week with several new products to demonstrate.  If you are there, please stop by and introduce yourself.  During that time, online orders may be delayed, but don’t worry – we will get to them as soon as we get back home.  As a preview, here is a video of the Interlocking In A Box prototype.Read More...

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One of the new projects we are working on is an “Interlocking In A Box” – a simple, yet flexible piece of signal logic designed to control an automatic interlocking for a diamond on a model railroad.  The idea came from one of the mail lists I’m subscribed to and we have been working on refining the definition and designing the signal logic over the past several months.  I figured now would be a good time show everyone where we are headed and maybe get some feedback.



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