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Know Before You Make Your Shunt Selections

S&C Distribution Company has moved dramatically beyond conventional head and base of rail clamp shunts because signal needs extend far beyond these two basic products. In the process, we have become aware of a wide range specialized needs relating to freight railroads, rail transit systems, electrified railroads and industrial railroads in North America and around the world. These needs include zero ohm shunts to support track work, efficiency tests, etc, and resistance values for various signal shunting purposes, on-track conditions, connection to the rail options, even down to such details as the length of the T-Screw. Because the variables are so broad, they are difficult to address in a website. Our people are trained to walk you through the options quickly, getting you to the point of decision without a lot of delay.

One benefit of having a collective 250 years, plus of railroad signal experience guiding our shunt design effort is that we well understand the needs and work environment of commissioning and testing (C & T) shunts. We understand the needs for a variety of resistance values and for the accuracy of resistance values, clamp-to-clamp. We have learned of the effects of unbalanced track circuits on C&T shunts and have found ways to mitigate the damage. Shunt inductance is a significant issue if the circuits you are shunting are AC, such as cab signal system, audio overlay or motion-responsive circuits and we know how to build shunts to accommodate these applications. We understand the need for shunt long-term durability, reliability and repairability, and our products reflect these understandings. We consider C&T shunts to be ruggedized instruments, not simple hand tools and every aspect of these products has an engineering justification.

Instruments typically carry serial numbers to allow traceability from the manufacturing process through the product’s entire service life. Each of our shunt products, including Zero Ohm Shunts and Track Jumpers, has its own serial number. Each of them is tested for proper resistance value or values and that data is recorded by type and serial number before it is shipped. The test records are retained in perpetuity for later reference. Our shunt products you have purchased have identities as do all the other instruments in your inventory. In fact, so much care has been given to our shunts in the design and assembly processes that we consider them calibrated. A label on each shunt so-states.

At S&C Distribution Company, component selection and assembly procedures for our shunts, track jumpers,
etc., result in products that are calibrated to the required values. Each shunt is tested for proper resistance
value prior to shipment, and the value recorded, by Serial Number in a perpetual log. A label, indicating that
the Shunt has been calibrated appears on the Resistor Bracket. In the case of Zero Ohm Shunts or Track
Jumpers, the “Calibrated” label will be applied to the cable, under a sleeve adjacent to a rail clamp.

Part of serviceability is repair. Because we and our customers expect service life to be well beyond a year, every element of our shunt products is repairable. Instructions that accompany all shunts include sections on repair and repair parts are listed in the instructions. Further, when the need eventually arises, our support personnel are knowledgeable and will help you identify the parts you need to repair your shunt. We also offer a repair service for our shunts. Our shunts are not throw-away.

A concept we have pioneered is the desirability and need to confirm the clamp-to-clamp resistance value of shunts from time to time. How do you know your C&T shunt is still testing at the value it should? The fact that other brand shunts had, in one way or the other, changed from the resistance value they came with, drew us into the shunt business in the first place. We have developed a range of accessories that allow the use of our 344 Short Finder (which reads resistance in 100dth ohm steps) to measure the resistance value of your shunts, regardless of brand, from clamp to clamp. Contact us for details.

Because of their status as instruments, very early on in our involvement with C & T shunts, we adopted a concept recommended by a signal foreman of considerable knowledge and experience; that shunts should not be slung about and tossed into the back of a truck or into the corner of a tool bin, but transported in a carry bag. Today, we are well known for our strong advocacy of shunt bags, and offer an extensive array, to support the wide variety of shunt configurations we sell. Several railroads have responded to our recommendation by making standard
internal catalog listings include a shunt bag with each shunt.

Improved visibility of shunts, or special-purpose designation of shunts, can be achieved with shunt wire colors. Our shunt wires are available in safety orange, red, yellow and traditional black. S&C shunts are shipped with black wires unless otherwise specified.

Following sections provide base ordering references for the various types of shunts. The information you provide us can be detailed as follows.

Select resistance value or values: .06, .07, .10, .12,.15, .18, .20, .25, .30, .40, .50, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50 and 2.0. Use “15X” for 1.50 ohm value and “2X” for 2.0 ohm value. Up to five resistances can be included in one standard Resistor Bracket. Our Multi-Shunt can accommodate up to 10 resistances. All test nuts down equals Zero ohm resistance.

Black (B) Wire Is furnished unless requested otherwise. Other choices are Red (R), Safety Orange (A) and Brite Yellow (Y). To specify color add alpha character in parenthesis (B, R, A and Y) to ordering reference as discussed below.

Add Z to indicate Heavy Duty Shunt Carry Bag

Typical Ordering Reference for a 2-Resistance (plus Zero) Shunt, Black Wire, Base Clamps with Carry Bag: 506-(_ _)(_ _)BBZ For Example: 506-(06)-(25)BBZ

Additional resistances would be indicated by additional values in parenthesis, in series with those shown above. Note that the numbering of the “official” part number will vary from the sequence you provide us.

A unique and very specialized “shunt” is also presented in this section. It is a shunt-like AC/DC, Style C Track Circuit trouble-shooting tool. The lead product listing in the section titled SPECIALIZED SHUNT CONFIGURATIONS FOR FREIGHT & TRANSIT APPLICATIONS, this “shunt” greatly simplifies the process of identifying what has caused your AC/DC track circuit to fail.

The following sub-sections display the many C & T Shunt configurations we manufacture. This display communicates the range of our offerings and the depth of our understanding of this specialized product group.