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Track Circuits

We offer complete, building block Style C or AC/DC circuit systems to for switch fouling, OS and highway crossing warning uses.  Building blocks include an AC Signal Source Unit and a Track Power Unit the feed the terminating Track Diode.  Use of this concept, which operates on 8 to 15VDC, provides a circuiting solution that will continue to operate after commercial power has failed, as long as the stand-by battery has the capacity to power it.   Our use of a true square-wave AC signal creates optimum shunting characteristics for the track circuits.  Because of the very high voltage spikes that are generated by the square wave signal, shunting characteristics are superior to DC and even AC sine-wave signals.

Typical crossing warning applications include Island-Only and Three Track Circuit configurations.  Style “C”, AC/DC Track Circuits address several problems that relate specifically to Fouling (Figure 1) and OS Circuits (Figure 2) Circuits.  These problems and solutions include:

  1. Shunting sensitivity of AC/DC track circuits is superior, which can be especially helpful at lightly used industrial spurs and sidings.
  2. For Fouling Circuits, the single-ended circuit eliminates a long cable run or an equipment housing at the far end of the circuit.
  3. For OS Circuits, the key elements of the circuit (the AC power feed, “ACSU and TPU”; the track relay, “TR” and the Track Diode) can be distributed in such a way as to allow direct shunting, as opposed to indirect or foul shunting, throughout the OS circuit.  This configuration, as shown in Figure 2, also provides a positive check of the fouling jumper wires.  If the wires break, track relay will de-energize, indicating occupancy.



An Application Guide, complete with specifications of the circuit components is available from S&C Distribution Company covering Crossing Warning, Switch Fouling and OS Circuit use of the Style “C” concept.


AC Source Unit215B-2
Track Power Unit215A-1
Circuit Terminating Track Diode217D
40 Volt Surge Protecting Network for 215A-10 and associated 215B-2215A-18
Circuit Panel for a single track circuit for rack or backboard mounting, less Surge Network, for use as an Island Crossing Warning Circuit, a Fouling Circuit or an OS Circuit215-1020
Circuit Panel, above but with 215A-18 Surge Network built-in215-1021


Track Resistor Kit, 0.5 Ohm Relay   Ordering Ref:  215A-RK1                            

Track Resistor Kit, 2.0 Ohm Relay   Ordering Ref:  215A-RK2

Track Resistor Kit, 4.0 Ohm Relay   Ordering Ref:  215A-RK3