Thanks, Greg. I did not find a way to search for other threads. Based on the thread you sent I missed some other issues with the circuit.
I liked the relay less version included in that thread.
see earlier thread
cs.trains.com/mrr/f/744/t/246297.aspx
greg - Philadelphia & Reading / Reading
(moved from general discussion thread)
I enjoyed Larry Puckett's article about DCC and occupancy detectors.
I'm an old Electronics Engineer who was taught about current flow in circuits rather than electron flow. It took me awhile to be comfortable with the circuit description that Larry provided and I needed to rethink in terms of current flow to be happy with it and confirm that the circuit will work just fine.
One question that I have is the -9VDC at the bottom of figure 4 on page 57. Based on the text description of the circuit being powered by 9 volts should this be a ground connection rather than -9VDC?
It would be feasible to replace the relay with a couple of transistors to drive LEDs in the signal.
Regards - Amby N.