How to install block occupancy detection on a DCC layout
Divide the track into detection sections and feed each through a current-sensing detector, so your system and software know which sections are occupied.
- Time
- Half a day
- Difficulty
- Medium
- Cost
- Moderate cost
- Steps
- 7
- Checked
What you’ll need
- Occupancy detector(s) compatible with your system (e.g. LocoNet, s88, LCC or a JMRI-supported interface)
- Insulated rail joiners or a razor saw Search Amazon for razor saw model railway
- Wire in two colours Search Amazon for 22 AWG hook up wire
- Terminal strips Search Amazon for terminal block strip
- Multimeter Search Amazon for digital multimeter
- Optional: resistor wheelsets for rolling stock
As an Amazon Associate we earn from qualifying purchases. The Amazon links go to search results, so you can compare what’s available.
Before you start
- Turn off track power before cutting into wiring.
- If you leave analogue locos on a DCC layout, Digitrax notes they can cause cross-talk between detection sections.
Step by step
-
Step 1: Plan your sections first
Digitrax advises planning detection around the operation you want before cutting any gaps. For example, a signal needs to know about two sections ahead to behave like the real thing, and hidden sidings benefit from a section per road (BDL168 manual).
Next: step 2 -
Step 2: Choose your wiring method
Digitrax recommends direct home wiring: each power district and its booster electrically isolated, with a common return inside the district. A detection section is gapped on one or both rails and fed through the detector.
Next: step 3 -
Step 3: Cut the gaps
Gap the detected rail at each end of each section (insulated joiners or a fine saw cut). Keep the other rail as the common.
Next: step 4 -
Step 4: Wire each section through the detector
Run the feed for each section's gapped rail through its detector input, and connect the detector's common as its instructions show. Nothing else that draws track power may connect to a detection section, or it will always read occupied (Digitrax).
Next: step 5 -
Step 5: Connect the detector to your system
Link the detector to its bus (LocoNet for the BDL168, for example) and give it the power supply it needs. The BDL168 needs a separate 12–16 V AC or DC supply.
Next: step 6 -
Step 6: Make rolling stock detectable
Current detectors see locos because they draw current. For unpowered stock, fit resistor wheelsets; the BDL168 detects them, and Digitrax gives a typical zone sensitivity of about 22 kΩ.
Next: step 7 -
Step 7: Test every section
Place a loco in each section and watch the indicator or the sensor table in your software. Then test with a single resistor-wheelset wagon.
Tips
- Number sections on a plan and label each wire – it saves hours later.
- Outdoor layouts may need sensitivity reducing; Digitrax suggests resistors between section and common (1 kΩ halves the sensitivity).
Questions people ask
Do I need detection for simple DCC running?
No – it's only needed for signals, panels and automation.
What about RailCom?
RailCom-capable detectors can also report which loco is in a section, if your decoders and booster support RailCom (NMRA S-9.3.2).
Sources
Checked 18 October 2026. We wrote this guide in our own words, using:
- Digitrax BDL168 occupancy detector manual (digitrax.com)
- Digitrax DCS240 command station manual (digitrax.com)
- NMRA S-9.3.2 Bi-Directional Communication (RailCom), draft (nmra.org)
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Printed from dcctrainautomation.uk/guides/install-block-occupancy-detection/ · Checked 18 October 2026 · General information only. Follow the maker’s instructions for your own equipment, and keep mains wiring inside properly made, enclosed power supplies.