The Detective EL-4 from the Erie Signal Company

• Easy to Install
• Works with Digital Command Control, DC or AC
• Runs on 12-16 volts AC or DC
• No Need for a Separate "Filtered" Power Supply
• Compatible with Any Scale (Z, N, HO, O, and more!)
• Output Controls Anything You Want

"The Detective" EL-4 senses small changes in current flow within a section of track to which it is connected. It works with AC, DCC, and conventional DC throttles.  It detects anything drawing current, like an engine, a lighted passenger car or caboose but doesn't slow down the train like traditional current-sensing circuits do. There's a time delay to prevent the circuit from "hiccupping", so it stays "detecting" for a couple of seconds. The circuit board is only 1.1" X 2", and uses very few parts - less stuff to go bad and can be mounted on or under the layout. Its output is a relay, to control almost any accessory you choose to use it with. Easy to wire, the Detective runs on 12-16 volts AC or DC so no "filtered" power supply is needed. Illustrated instructions for the Detective are included.

Additional Features of the Detective Track Circuit

• Works with all ambient layout room lighting, unlike photocells
• No infrared beams to align
• Unlike current sensing circuits using diodes, train won't slow down
• Installation is easy, just two wires to connect to power supply
• Use output to turn on or off circuits such as signals, block occupancy lights, panel lights, crossing signal flashers
• When used with resistive wheelsets on non-lighted cars, will detect the entire train
• Will detect DCC equipped locomotives even when headlamps and sound are turned off  

Watch the Detective Track Circuit in Action

We recently visited a model railroad that uses several of Erie Signal Company's EL-4 Detective circuits. These track circuits detect whether or not an isolated electrical block is occupied, then controls a separate relay to operate the signals.

From another angle, we can see how well the Detective track circuit works at detecting these HO scale locomotives as they approach and enter an interlocking on a user's CSX model railroad.