switch machine contacts


Hi all; I have several twin coil switch machines with extra contacts for lights or signals . I can not for the life of me figure out how to use them to power a lamp on my control panel. I would like to have a light lit for the straight route when I push that button,and one for the alternate route when I push that button. I finally figured out how to wire the machines to throw the switches but can't figure out the extra contacts. I am probably the dumbest person on electrical wiring in the hobby,so a few pictures or diagrams would be heaven sent.

thanks to all who reply Larry



Contacts---with a warning

The warning--I'm going from a faulty memory--it's old and tired, without a twin coil any where in the house.

As I remember each group of contacts was a single pole double throw configuration.  I remember 4 groups of contacts on some of the machines.  The current rating is most likely about 1 amp.  I would derate this to 500mA or less for longevity.  Inspect the switch machine before it is installed to determine how the contacts work.  Take some time to understand this. 

To wire the lamps, pick out one group of contacts to use,  The center contact of the group is the common contact and should be connected to the lamp power common.  The lamps should be connected to the other two contacts of the group.  Throw the machine by hand to see which contacts are mated when the turnout is thrown in a certain direction.  Connect the appropriate lamp wire to that contact.  Repeat for the other lamp.  Don 't worry to much about getting the lamps backward--there's a relatively easy fix.  Hook up the other side of the lamp to the lamp power supply terminal.  If you are unsure, set up one on the bench to see how it works, try it out and then install on the layout

Check operation,  If the lamps are backward then change the wires at the lamps--it's easier than crawling under the layout.

If you are not familiar with soldering, get a soldering iron, solder and practice.  Do not use a solder gun.  The contacts are too small and the quality of solder joints with a gun are suspect,  No electronics manufacturing company that I know allows one on the assembly floor. 



dfandrews's picture

Kemtron machine contacts

Here is a photo of the Kemtron style machine.  In addition to the two sets of double throw contacts side-by-side, there is another double throw contact set at the other end with the center pole in contact with the machine frame.



Rincon Pacific Rwy, 1960.  HO scale std. gauge - interchange with SP.


UPWilly's picture

If Kemtron ...

If your dual-coil switch machines are Kemtron or one of the other two or so "copycats", then here is the instruction sheet:


I had an N Scale layout using these in '72 and they worked well (just need to get used to the "thunk" when energized). I liked them so much, I bought a few on EBay used and new. Back when they were very popular, the retail price was around $1.95 - they have appreciated in value, partially due to inflation.

There are three things one should be cautious with using these:

1. Be sure the contacts are well aligned - there are screws that can be loosened and tightened to facilitate this.

2. The metal tab on the cam mechanism that moves the common pole of the contact set needs to be insulated to prevent shorts. On good machines, there is a thin clear plastic sleeve that fits over the tab for insulation.

3. If using the alternate contacts (illustrated in the manufacturers instructions for powering the turnout points), then the metal frame of the mechanism will have one leg of power to it.

The above applies, if you are using DC (analog). If you are using DCC, then there are other things to consider, i.e. "Frog Juicers", et al.



Bill D.

N Scale (1:160), not N Gauge. DC (analog), Stapleton PWM Throttle.

Proto-freelance Southwest U.S. 2nd half 20th Century.

Keep on trackin'



my switch machines are rix

my switch machines are rix and lambert, I thank you for the input I will copy it just in case.



UPWilly's picture

A suggestion

Larry, have you tried contacting Rick Rideout at Rix Products ? The necessary information you need does not appear to be on the web site, but you might want to send a message asking for a diagram and/or some explanation. His email address is:



Bill D.

N Scale (1:160), not N Gauge. DC (analog), Stapleton PWM Throttle.

Proto-freelance Southwest U.S. 2nd half 20th Century.

Keep on trackin'



Minimum Switch Machine wiring diagram.


Before going off and wiring all your machines and indicators with harnesses that have to carry the high current for the switch coils plus the current for your indicators (5 or 6 wires per switch machine), I'd just like to suggest the wiring I used in the 70s before the advent of DCC.  Basically I used the frog polarity switch to 'enable' the other coil while allowing a trickle current through the enabled coil to light an LED through a limiting resistor.

  Here is how it works.  As shown the switch machine is set to the main route.  Notice that the frog polarity contacts allow a trickle current  (10 Ma or so)  To flow through the diverging coil.  10Ma isn't going to do much to that coil but the 'Main' indicator will light. Pushing the 'diverging' button allows a surge of current to activate the diverging coil and effectively turn itself off, allowing the trickle current to flow through the 'Diverging' indicator.  Now pushing the 'main' button the reverse occurs.

What about the frog?  You can use the auxiliary contacts for that except I would suggest you put a 12 volt auto brake lamp in series with power to the frog.  This will prevent your circuit breaker from shutting your layout (power district) down.  Should the switch be set against an engine the engine wheels will short the throttle supply.  However a 12v auto brake light will provide enough resistance to prevent this.  What is neat is the characteristic of the lamp.  When the lamp element is cool its resistance is low and a speeding train wont even feel any voltage drop as it barrels over the frog.  (Watch a brake light on a car.  It kind of fades on and off - unlike an LED).  Also the engine motor will be in series with the lamp.  This will also allow time for the engine to safely cross the frog.  The auxiliary contacts on the swich machine can safely handle the current for such a short time.  Try it and good luck.





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