Occupancy Detectors

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Summary: Occupancy Detectors are used as part of a signaling system to detect the presence or absence of a train. Their feedback can control signals or lamps on dispatcher's panels, allowing for smooth, prototypical train movements. A number of commercial versions are available from various DCC manufacturers. Many suppliers of DCC systems also have accessory lines including detection devices. Some are also available as do-it-yourself projects



  • LocoNet Occupancy
  • 16 detection sections
  • Three amps per section

BDL16: Released in 2000 BDL162 replaced it in 2002, upgrade kit was available. Superseded by the BDL168 in 2004.

  • Works with the DS64 or SE8C
  • * Also works with the DS54
  • LocoNet detection for 4 occupancy detection sections via the DS64 or SE8C stationary decoders
  • Not recommended for use with SuperSonic decoders
Main article: BD4N
  • Eight Amp Occupancy Detector
  • Adjustable trip threshold
  • Compatible with the BDL168
    • Compatible with the DS64 and SE8 modules for connection to LocoNet
  • Status LEDs, expandable for optional LT5 or panel indicators via headers
  • Can drive most signal systems or interfaces
  • Plug and Play
  • Transponding Receiver Add-on for BDL Series Detectors
  • Adds up to eight transponding sections to the BDL168
  • RD2 Remote Sensing Diodes for BDL16 series occupancy detectors
  • Remote sensing of two detection sections
  • Eliminates the need to run heavy wire between the BDL168, BDL16 or BDL162 and remote track sections

Detection and Power Management

Main article: BXP88
  • LocoNet Occupancy Detector
  • * occupancy
  • * transponding
  • * track power
  • Eight Detection Sections
  • Transponding
  • * One per detection section
  • Power Management
  • * One for each detection section
  • * Three Amps per section
  • * Eight Amps total
  • LED output for indication of Section occupancy, Transponding, and power status.
Main article: BXPA1

Additional connections:

  • Outputs for opt-isolated occupancy detector output
  • Manual power control
  • Status indication


Lenz has the LB101, which contains two independent occupancy detectors.


BD20 Block Detector

Detects presence of a locomotive a section of track. Also works with resistor wheel sets NO Switch, triggered by current flowing through a current transformer Logic Output Must be used with an AIU to interface with a Signal


Auxiliary Input Unit (AIU01)

  • connect up to 14 external devices to the Command Station via the Cab Bus
  • Switch contacts
  • Block Detectors (BD20)
  • Other sensors

DCC Specialties

Block Watcher

  • Solid State: Fast, all solid-state design with reliable quiet electronics.
  • No Power Supply Needed
  • Very Low Voltage Drop: The resistance is less than 0.060 Ohms, very small voltage drop.
  • Adaptive Block Leakage Detection: Electronically determines the amount of leakage current in the block when power is turned on. The current can also be set with a CV value up to about 130 mA.
  • Stabilized Setting for Current Trip Level: This prevents the block detection from fluttering on and off when the current is near the trip level.
  • Block Detection Option: Block detection can be turned on with an Accessory Command for testing signals even with nothing in the block. This feature can also be used to turn the signals red to protect a crossing.
  • Block Detection Output Isolated from Track Power: The output switch is totally isolated from the track power. This eliminates many wiring problems when combining signal circuits and track power.
  • Outputs for LED Indicator: A single LED output can be used for a remote location.


These are primarily designed for use with Analog AC or DC operations, but can be used with DCC.

BD-2 Block Occupancy Detector

  • Current sensing train detector circuits
  • Can provide 2 color (Red/ Green) signal outputs for an isolated block of track.
  • BD-2 and BD-2HD can be used with common rail wired AC or DC track power
  • Will work with most Command Control systems
BD-2HD Block Occupancy Detector

For S Scale and larger.

BD-1 Heavy Duty Block Occupancy Detector

  • Optical Detection system
  • 250mA output
  • Can power lamps or LEDs

BD-1HD Heavy Duty Block Occupancy Detector

  • Optical Detection system
  • 500mA output
  • Can power lamps or LEDs


  • ECoSDetector
  • ECoSDetector Standard
  • ECoSDetector RC
  • ECoSDetector Extension

Every ECoSDetector can be directly connected to the command station via ECoSlink bus. Compatible with all ECoS command stations and the Central Station (updated with software upgrade by ESU)

The galvanic isolation of the bus systems and the command station.

All ECoSDetector modules will be detected automatically by the command station. The configuration can be also carried out directly with the command station after installation.


16 sections, up to 3A Reed switches, detection track sections, push buttons or toggle switches can all be connected to the inputs. Four RailCom sections Opto Isolated

ECoSDetector Standard

This unit is for the s88 bus

ECoSDetector RC

Monitor 4 track sections with RailCom technology to determine if the track is occupied and which train is located there.

RailCom capable multifunction decoders required.

ECoSDetector Extension

  • Each ECoSDetector can be supplemented by an ECoSDetector Extension module, which offers 32 transistor outputs.
  • Each one of the 32 outputs provides up to 100mA max. Open collector outputs, connect either small light bulbs or LEDs with current limiting resistor directly to it.
  • The total current of all outputs must not exceed 1.5A.
Track Occupancy and Block Signals
  • Display the state of each section externally.
  • Alternatively, track sections occupancy displayed using a block signal (red/green).
  • The transistor outputs of the ECoSDetector Extension module easily programmed via your ECoS command station.


Quad Occupancy Detector

  • Works with both analog and Digital Command Control
  • Available in both kit form, bare PCB, and assembled.
  • Can be constructed as a single, dual, triple or quad detector.

Resistor wheel sets, such as those from Logic Rail Technologies, are required.



Block Occupancy Detector For DCC
Schematics available
PCBs can be ordered from the site.

Further Reading