ISS is a dealer for multiple DCC manufacturers. We offer different detectors at various prices. We have used and installed all of the detectors listed.

NCE BD20. $12.00 ea.

NCE BD20 Block Occupancy Detector

The BD-20 block detector module is normally used to indicate the presence of a locomotive, caboose or other rolling stock in a track section by sensing electrical current drawn by that rolling stock. Locomotives will naturally trigger the detector because they draw current through their DCC decoder. Unpowered rolling stock will not trigger the detector unless equipped with some means of drawing current from the rails such as lights or resistor wheel sets.

The BD20 needs to be as close to the section being detected as possible to avoid false detection triggered by long runs of cable. For the BD20 to work correctly ALL feeders for the section being detected must go thru the BD20. The best practice is to have one BD20 per feeder, and only one feeder per section of track. That section should be isolated from all other sections by using gaps or insulating rail joiners. 

The BD20 acts like a normally open switch that gets triggered by sensing current going thru the coil. In a typical application you connect the outputs of the BD20 to something (Logic + 5 to 12vdc) that will react to a ground short.

DCC Specialties BlockWatcher. $26.00 ea.

DCC Specialties and Integrated Signal Systems (ISS) collaborated to develop and design the BlockWatcher. The need was due to the fact that at the higher amperages required by high density users, most existing products either create a substantial voltage drop or can become unstable.Block-Watcher

This detector puts the power of a microprocessor to work analyzing the current feed to the rails. This detector has been designed to eliminate many of the installation problems associated with the installation of signal systems. The Block Watcher comes ready to install, all you have to do is to connect it between the DCC booster or circuit breaker and the rails. Then connect the detector output switch to your signal system.

It can not only be used as the basis of signaling systems, but can also be used to indicate occupied blocks or triggers for Stop-On-DCC decoders. The Block Watcher is powered from the DCC input power and eliminates the need for an added external power supply. The output is optically isolated so the signaling system can be separate from the DCC signal and thus minimize the interference with operation of the signal circuits. The detector will handle up to 20 Amps of DCC current. An automatic adjustment for leakage current up to 130 mA is provided. Detection output terminals are available for a switched output and remote LED block detect indication. The bi-polar output can be used with any signaling system using less than 30 Volts and will switch up to 1 A of current.

  • All Solid State Operation: Fast, all solid-state design with reliable quiet electronics.
  • No Power Supply Needed:  Develops power from the DCC input connections.
  • 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.




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