Circuitron’s Application Notes are supplements to the instruction sheets provided with our products.  They provide further clarification (and in some cases, wiring diagrams) of specific issues or unique methods of utilizing our products.  Some of these Application Notes may be fairly “rough” sketches and may, in fact, be untested.  But they are all believed to work.   Let us know if you have any problems.  These Application Notes are catalogued with a 4 digit number, usually followed by a 2 digit suffix.  Notes numbered under 1,000 are generally generic applications that apply to potentially a wide range of our products.  More specific Application Notes will have the product part number incorporated into the note, ie. 5400-01 or 6000-07, referring to notes specific to the AR-1 and TORTOISE™.  These Application Notes are indexed here in numerical order, and as a general rule within a product listing, this means that the higher the number, the more recent the note.  Clicking any Application Note number will take you to a .PDF of the document that you can read or print out.  If a number is light in color, it means the Application Note has not yet been converted to PDF and made available here.  Check back later.  And if you feel any part of any of our instruction sheets could be enhanced by a new Application Note, please send us an email at:   


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AN-0001    Activating Circuitron Detection Circuits with External Switches

Using Reed, Pushbutton or Toggle switches for manual activation of our Opto-electronic detection and reversing products.       

AN-0002    Achieving 2 aspect Output from any Circuitron Detection Output

How to add Red AND Green LED indicators to Circuitron Detection Outputs for Signals or panel indicators.

AN-0003    Adding Opto-Sensors to any Circuitron Detection Input

Up to 2 additional sensors may be added to each input.  Here is how to do it right.

AN-0004    Automatic Slowdowns and Startups

AN-0005    About Light Emitting Diodes

Light Emitting Diodes are versatile, efficient light sources.  Here is how to use them with our products and how to choose a safe value current limiting resistor.

AN-0006    Desoldering—How to properly and safely un-do a soldered joint.

AN-0010    Panel Indicator Lamps and LEDs—How to install and what to use.


AN-5400-01       Using the AR-1 for Reverse Loop Applications

Although the AR-1 was not designed specifically for reverse loop   applications, there are situations where it can and cannot be used.


AN-5501-01       Driving a Bi-Color LED from Block Detector Outputs

Although the BD-1 and BD-2 were designed to drive separate Red and   Green lamps or LEDs, they are capable of driving a single Bi-Color LED from their outputs using two extra resistors.

AN-5501-02       Detection on Sidings with the BD-1 and DT-4

The BD-1 provides bi-directional detection for one full block on a single track.  But what do you do if you have sidings or spurs diverging within the block?


AN-5701-01       Increasing the Volume of the DH-1 Diesel Horn Circuit

Although the DH-1 has adequate volume for most layouts with the included small speaker, there are situations where more “oomph” would be desirable.  Here are some suggestions.


AN-6000-01       Off-Center Mounting of the TORTOISE™

How to mount a TORTOISE™ if you have an obstruction in the way.

AN-6000-02       Using the Internal SPDT Switches of the TORTOISE™

How to wire the TORTOISE™ to provide power to the frog of a turnout, to implement power routing or to power a trackside signal or panel lights.

AN-6000-03       Using the TORTOISE™ with Peco Turnouts

Peco brand turnouts have a factory over-center spring.  Here’s the best way to use a TORTOISE with them.

AN-6000-04       Edge Connectors for use with the TORTOISE™

Suggestions on where to purchase TORTOISE ™ compatible edge connectors and the specifications you need to be aware of.

AN-6000-05  Using the TORTOISE™ to drive crossing gates

The TORTOISE™ is ideal for driving animation accessories such as crossing gates and semaphores.  Here’s how to use a DPDT relay or the Circuitron ER-2 to control the TORTOISE™.

AN-6000-06  Locked TORTOISE™ Switch Machines

Once in a great while, a TORTOISE™ is received in a locked condition.  This results from a blow during shipping but the “cure” may surprise you.

AN-6000-07  Adding Light Emitting Diodes to the TORTOISE™ for panel indications    It is extremely easy to wire a pair of “back to back” LEDs to the TORTOISE™ motor to provide panel indications.  Here’s how to do it.

AN-6000-08  Using Bi-Color LEDs on your control panel with TORTOISE™s    Although it might seem like a good idea to use Bi-Color LEDs on your control panel with the TORTOISE™,  there are some things to consider.  This will explain how to do it….. And why you might not want to.

AN-6000-09  The TORTOISE™ and DCC Control

Controlling the TORTOISE™ from your DCC cab.

AN-6000-10  Non-Derailing turnout control of your TORTOISE™

The TORTOISE™ can provide a Non-Derailing function when a train approaches.  Here are a number of ways this can be accomplished including DCC controls.

AN-6000-11  Adding Filter Capacitors to a DC power source

When powering the TORTOISE™ from an unfiltered DC source such as might be taken from a power pack’s DC accessory terminals or a “steering diode” AC source as described in the TORTOISE™ instructions, an audible hum may be generated by the stalled machines.  If numerous machines are all mounted on a single surface such as a sheet of plywood, the sound may be amplified and be objectionable.  Here is how to add filter capacitors to these types of power supplies.