Re: RC snubbing in a DCCOD occupation block

Vollrath, Don <dvollrath@...>

To compensate for twisted pair wiring capacitance AFTER a block detector see



From: WiringForDCC@... [mailto:WiringForDCC@...] On Behalf Of SBB_BLS_Bahnen@...
Sent: Tuesday, April 22, 2014 3:16 PM
To: WiringForDCC@...
Subject: [WiringForDCC] RC snubbing in a DCCOD occupation block


I was installing some RC snubbers on the remaining track buses yesterday, and by chance installed one on a bus that feeds power to an occupancy detection block that is monitored by one of Bruce Chubb's DCCOD circuits. As soon as I powered on to test that everything was still working properly, I noticed that the DCCOD LED connected to its output was lit even though no train was in the block. I knew this would happen but wasn't thinking when I installed that snubber. When I removed the snubber, the LED went off as expected.

The track bus that feeds this occupancy block is a branch from the a main track bus connected about 10 feet from the open end of that main bus. The main bus at the open end is terminated with its own snubber. My question is whether that snubber should be sufficient for even the branch bus that feeds this occupancy block. I don't have access to an oscilloscope, so I can't verify the DCC waveform on that branch bus.

For reference, info on the DCCOD can be found here:




Timothy A Johnson, Tucson, AZ (
European Train Enthusiasts, Central Arizona Chapter (

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