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To power the 6009 http://www.tandem-associates.com/lionel/lionel_trains_6009_track.htm or 6029 http://www.tandem-associates.com/lionel/lionel_trains_6029_track.htm uncoupler track with constant voltage would require modifying the track.
The wire from the coil to the center rail would need to be unsoldered, and a wire from the external power source soldered to the coil lead. The solder joint needs to be wrapped in electrical insulating tape to prevent the joint from shorting out.

If you are using a second transformer to power the uncoupling magnet, the transformer needs to be phased to the track transformer, and a ground wire added to the outside rails of your layout, usually through your track lockon. Adjust the voltage for satisfactory performance.

If you are using the accessory terminals of a transformer, hook the new coil wire to a voltage tap that gives satisfactory performance, usually 14-16 volts. No additional ground wire is needed in this case.

The push button for operation remains wired the same.

Larry