Testing Shunts & Switch Obstruction Gauge



FRA Rules That Apply

Satisfy Requirements of FRA Signal Rules With Our Test Equipment
Rule # Rule Description S & C Equipment
234.229 Shunting Sensitivity Tests Model 340 Time Activated Testing Shunt
506 Series Testing Shunts
234.259 Warning Time Tests Model 340 Time Activated Testing Shunt
236.51 Rule for Track Circuits Model 340 Time Activated Testing Shunt
506 Series Testing Shunts
236.56 Rule for Shunting Sensitivity Model 340 Time Activated Testing Shunt
506 Series Testing Shunts
236.104 Shunt Fouling Circuit Test 506 Series Testing Shunts


Shortcut to Specific Products

Notes on Shunt Quality

While seemingly basic, uncomplicated products, testing shunts are critical to the proper operation of the signal system. In keeping with this criticality, every Shunt manufactured by S&C Distribution Company, including zero ohm shunts, is assigned a Serial Number and is tested for proper value or values prior to shipment. The test results are recorded by Serial Number, in a permanent record, for traceability.

Further, every aspect of our Shunt design has an engineering justification. Being aware of significant shortfalls in resistance accuracy and durability of other shunt products, we have reviewed our designs to eliminate, or design countermeasures for, every point where it would be possible for resistance to accumulate. These efforts have resulted in Shunts that, hand tight, will shunt your track circuits "the first time, every time", according to our many satisfied customers. On the subject of durability, one railroad considers our Shunts "ten year service life shunts".

How to Specify Shunt Resistance

With each of the below listed types of testing shunts where resistance values are involved note that there is one ordering reference for each type of connector (head-of-rail clamp, base-of-rail clamp), regardless of shunt resistance. Also note that within that ordering reference are blank spaces represented by dashed underscore lines ( _ _ ). This group of blank spaces is where you indicate the resistance value desired. Where two resistances are available in one shunt, two sets of dashed underscore lines are presented.

We have configured the ordering reference in this way because we offer an extensive line of standard resistances, can produce a shunt with virtually any resistance value you might request. As well as a shunt with multiple resistances values. Rather than create pages of ordering references, the only variation to which would be the resistance value itself, we let you fill in the blanks as appropriate. At present our standard resistance values are:

  1. 0.06 ohms
  2. 0.10 ohms
  3. 0.15 ohms
  4. 0.20 ohms
  5. 0.25 ohms
  6. 2.00 ohms

When completing the ordering reference to place your order, fill in the blanks with numbers in the exact sequences shown above. Do not include the decimal point. For example a 0.06 ohm shunt value would read: 0 6. If you need a resistance other than one of the values listed above, simply specify the value in the same sequence as shown. For example a 0.25 ohm shunt value would read: 2 5. If the value you require is two ohms (2:0) show it as "2X". Note that if you order a value other than one of those listed above, the lead time is 45 days to 60 days ARO. Please contact us for ordering instructions. Otherwise our Shunts are generally shipped from stock.



Shunt Carry Bags

For transporting and storing Shunts. Heavy canvas with zipper. Standard size for all conventional Shunts; larger size for Imbedded Rail, 14 inch and 24 inch Fast Shunts.

ORDERING REFERENCES
Description Part Number
Standard Size Bag 506ZB
Larger Bag 506BZB
Safety Orange Bag f/14" Handles 506ONBZB
Safety Orange Bag f/24" Handles 506ONBZB-24


506 Series Shunts Introduction

S&C Railroad Grade Shunt Clamps bring strength and conductivity that have not been achieved in shunt clamps before, but should have been. They also introduce a new concept; maintainability, that does not compromise shunt reliability. And, to address today’s conditions, our head-of-rail clamps have the widest reach and longest legs to permit accommodation of the worst lipped-over rail, yet will clamp to rail sections from 70 lb. to 140 lb. This design also results in a clamp that does not spread as it is tightened on the rail, maintaining a zero ohm connection.

Our Base-of-Rail Clamp (see photo at left) has been reconfigured to be “Easy-On”. The Connector for the shunt wire also serves as a handle, permitting the user to shove the Clamp onto the rail with a very minimal effort. Usually no digging away of ballast is required. Additional features of the “Easy-On” base-of-rail clamp are: that it is shaped to match the rail base to prevent “walking”, clearance requirements between rail and ballast have been reduced to the absolute minimum, and the connector tip is an integral part of the clamp, eliminating a point of potential parasitic resistance.

Both Clamps and their T-Screws and Connectors feature 55-60 Rockwell C heat-treat hardening and hard tool chrome plating for durability and resistance to rust and corrosion. These Clamps are available for purchase separately.

ORDERING REFERENCES
Ref Description Part Number
1
Easy-On Base-of-Rail Clamp, complete 340-100-18
2
Lock-Down Easy-On Base of Rail Clamp, complete 340-100-18NW
3
Head-of-Rail Clamp, complete 340-200
4
Lock-Down Head-of-Rail Clamp, complete 340-200NW


506NW Series Shunts for M/W and Operating Department Applications

Our “NW” Series, zero ohm, hardwire shunts are intended for use by maintenance of way personnel to clear highway crossing signals during track maintenance operations and by operating department personnel when conducting efficiency or signal response tests of train crews. No. 6 AWG welding cable is used to provide maximum conductivity, flexibility and ease of use. Shunt wires are available in safety orange, red and black. These Shunts come with S&C railroad-grade clamps with special, lock-down nuts and washers to help insure stable, long-term connection to the rail.
ORDERING REFERENCES
Description
Black Wire Red Wire Orange Wire
0 Ohm w/Base-of-Rail Clamps 506-00BNW 506-00RNW 506-00ONW
0 Ohm w/Head-of-Rail Clamps 506-00BNWH 506-00RNWH 506-00ONWH


506 Series Zero Ohm Testing Shunts

Zero ohm, hardwire testing shunts are a basic signal testing tool. Highly flexible No. 6 AWG welding cable is used to provide maximum conductivity, flexibility and ease of use. Shunt wires are available in bright orange, red and black. These Shunts come with S&C railroad-grade base or head-of-rail clamps or file handles.

ORDERING REFERENCES
Description Black Wire Red Wire Orange Wire
0 ohm w/Base Clamps 506-00BB 506-00RB 506-00OB
0 ohm w/Head Clamps 506-00BH 506-00RH 506-00OH
0 ohm w/File Handles 506-00BF 506-00RF 506-00OF


506 Clamp Testing Shunts

Rugged, traditional, clamp-type testing shunts for adjusting and testing track circuits. Unique design assures extremely low probability of change of resistance values within the shunt assembly. Switchable between common testing values and zero ohms with test nut. Very close electrical tolerances make these tools highly accurate. Head-Of-Rail Clamps accommodate lipped-over rail and an unusually wide range of rail sections; 70 to 140 lb. Can be purchased with one or two resistances and zero ohms in one shunt.

ORDERING REFERENCES
Description 1 Resistance 2 Resistances
Base-of-Rail Clamps 506-( _ _ )B 506-( _ _ ) ( _ _ )B
Head-of-Rail Clamps 506-( _ _ )H 506-( _ _ ) ( _ _ )H


506CB Series Head of rail Clamp Testing Shunt

A shunt configuration developed in response to customer request, these clamp-type testing shunts depart from the traditional by placing the Resistor Bracket on a standoff from one of the head-of-rail clamps. This design moves the Resistor Bracket out of the middle of the shunt wire, significantly reducing the potential of the Bracket to snag, being damaged, etc. It also makes it easier to vary the resistance values, by placing the adjustment point at top-of-rail height, rather than on the ground. In addition to being unique, these shunts are built to the usual S&C specification, heavy-duty, railroad grade, highly accurate and reliable.

Ordering References
(Insert resistance value or values .06, .10, .15, .20, .25, 2.0, where blanks in parenthesis are shown, omitting decimal. Use “2X” for 2.0 ohm value).

To have a heavy-duty, protective, canvas Shunt Bag furnished with your Shunt, add a “Z” behind the “H” in the ordering reference.

ORDERING REFERENCES
Description Part Number
Single resistance & Zero 506CB-(_ _)H
2 resistances & Zero 506CB-(_ _)(_ _)H
3 resistances & Zero 506CB-(_ _)(_ _)(_ _)H
CB Clamp with Mounting Bracket for Resistor 340-200CB


506-600 Clamp Shunts w/Open

Rugged, clamp-type testing shunts, with special "Open" option, for adjusting and testing track circuits. Shunt can be opened without removing clamps from the rail. Unique design of the overall shunt assures extremely low probability of resistance variations within the shunt assembly. Switchable between common testing values, zero ohms and open with test nuts. Very close electrical tolerances make these tools highly accurate. Both base-of-rail and head-of-rail clamp versions are available. Our Railroad Grade Head-Of-Rail Clamps accommodate lipped-over rail and an unusually wide range of rail sections; 70 to 150 lb.

ORDERING REFERENCES
Description 1 Resistance 2 Resistances
Base-of-Rail Clamps 506-( _ _ )OB 506-( _ _ ) ( _ _ )OB
Head-of-Rail Clamps 506-( _ _ )OH 506-( _ _ ) ( _ _ )OH




506-120 Track Jumper

Track Jumpers are used to facilitate track maintenance operations. They are particularly helpful in keeping crossing warning systems from being unnecessarily activated. Extended length allows the bypass of insulated joint replacement activities. No. 6 AWG welding cable is used to provide maximum conductivity, flexibility and ease of use. Wire insulation colors available include black, red and orange. Comes with S&C railroad grade base-of-rail or head-of-rail clamps. Track Jumpers with Base-of-Rail Clamps are furnished with "NW", lock-down type of clamps. Twenty foot length listed here. Lengths available range from six feet to 350 feet.

ORDERING REFERENCES
Description NW Base Clamps Head Clamps
Track Jumper, 20ft, black wire 506-120BB 506-120-BH
Track Jumper, 20ft, red wire 506-120 RB 506-120RH
Track Jumper, 20ft, orange wire 506-120OB 506-120OH




506 File Testing Shunts

Rugged, file-type testing shunts for making quick shunting tests or for adjusting and testing track circuits in flush rail environments. Can be switched between common testing values and zero ohms. Very close electrical tolerances make these tools highly accurate. Can be purchased with two resistances in one shunt.

ORDERING REFERENCES
Description Part Numbers
File Shunt w/one resistance 506-(_ _)
File Shunt w/two resistances 506-(_ _) (_ _)


506P Series Probe Testing Shunts

A new way to connect testing shunts to the rail temporarily and easily. 506P Shunts (AC-Only and single resistance shunts shown to the left) utilize the probe concept, providing railroad-durable 12.5 inch Probes (including handle length with tips that are file hard. The 12 inch length makes reaching rail to rail with enough leverage to effect a reliable shunt doable, and the hardened tips insure long service life. Probes are hard tool chromed after fabrication and heat treating for resistance to rust, corrosion, etc.

Our Probe Shunts are especially helpful in making "rolling" shunt and shunt fouling tests. Unique design assures extremely low probability of resistance variation within the Shunt. Very close electrical tolerances make these tools highly accurate. Every Shunt furnished by S&C Distribution Company is factory tested for proper resistance value(s). Each Shunt is serial numbered and the values of resistance are recorded with the serial number for traceability.

Probe Shunts come in several configurations: Zero ohm (hardwire), switchable with test nut between Zero ohm and one or two common testing resistances and in an AC-Only configuration for specialized crossing warning system testing applications.

ORDERING REFERENCES
Description Part Number
Hardwire Shunt 506P-00
Single resistance & Zero 506P-(_ _)
2 resistance & Zero 506P-(_ _) (_ _)
AC-Only Shunt 516P-AC
Handle, w/Probe 506P-1
Probes, only, 1 Pair 506P-2


516 AC-Only Testing Shunts

AC-Only Shunts can permit the set-up and testing of audio frequency and motion responsive track circuits without disrupting the operation of DC train detection track circuits. When used safely and carefully (see instructions furnished with the Shunts) this capability can significantly improve a signalman's productivity and improve overall maintenance of crossing warning systems. A large, bright red warning label, incorporating key safety information contained in the instructions, is firmly mounted to the shunt cartridge. Shunts come with bright orange wire and either File Handles, Dual-Blade Handles, Warren Fast Shunt Handles (see following section for description of Warren Fast Shunt) and Head or Base-of-Rail Clamps. Note that, due to the safety implications should this Shunt be accidentally left on the track, we recommend against using this Shunt with Base-of-Rail Clamps.

ORDERING REFERENCES
Description Part Number
Shunt w/File Handles 516-F
Shunt w/Dual-Blade Handles 516-DB
Shunt w/Warren Fast Shunt Handles (14 in.) 516-WFS
Shunt w/Warren Fast Shunt Handles (38 in.) 516-WFS38
Shunt w/Head-of-Rail Clamps 516-H
Shunt w/Base-of-Rail 516-B


Warren Fast Shunt

A very old idea resurrected by S&C Distribution Company, in response to considerable interest from signalmen. This concept greatly facilitates making quick on and off shunts required for shunt fouling tests, series shunting during cutovers, and for making shunt tests to confirm circuit performance during required monthly, quarterly and annual tests. Come in two handle configurations: with operating handles approximately 14 inches (3.0 lbs) and 38 inches (6.0 lbs) long. Any shunt wire manufactured by S&C Distribution Company can be equipped with these handles.

ORDERING REFERENCES
14 in. Handles 38 in. Handles
Description Part Number Part Number
0 ohm, hardwire 506WFS-00 506WFS38-00
0 ohm and single resistor 506WFS-(_ _) 506WFS38-(_ _)
0 ohm and two resistors 506WFS-(_ _) (_ _) 506WFS38-(_ _)(_ _)
AC-Only Shunt 516-WFS 516-WFS38


506WFS Circuit Testing Shunt

The Model 506 Circuit Testing Shunt with Meter includes an S&C Warren Fast Shunt (your choice of 14, 24 or 38 inch handles) with your choice of resistances, and built-in meter leads, with an S&C, AC/DC digital, low-temperature (-40 degF) Voltmeter (PN: 506-802, see separate listing in the “Insulated Joint Testing and Track Circuit Testing” section of this website). Switching the Shunt between “Open” and the resistance value or values ordered, accurate track circuit tests are achieved in seconds.

The Fast Shunt allows you to move quickly between shunting points, while connecting effectively to even the rustiest rail. A thumb screw firmly retains the 506-802 Digital AC/DC Voltmeter in its Instrument Mounting Bracket. While the most common configuration includes the 0.06 ohm resistance, more than one resistor can be included in the Resistor Bracket (resistance options include: 0.06, 0.10, 0.15, 0.20, 0.25 and 2.0 ohms), depending on handle length selected. As indicated in the ordering reference table below, Retro-Fit Kits are available for converting your conventional Warren Fast Shunt to a Circuit Testing Shunt. Kits fit all Handles.

ORDERING REFERENCES
Ref Handle Length Description Part Number
12-5 14 in. Shunt with single resistance, Meter, Leads, Bag 506WFSS-(_ _)VZ
12-2 14 in. Shunt with single resistance, Leads & Bag 506WFSS-(_ _)LZ
12-1 24 in. Shunt with single resistance, Meter, Leads, Bag 506WFSS24-(_ _)VZ
12-1A 24 in. Shunt with single resistance, Leads & Bag 506WFSS24-(_ _)LZ
12-6 All Retro-Fit Kit, Meter, Leads, single resistance 506WFSSV-RFK(_ _)
12-4 All Retro-Fit Kit, Leads, single resistance 506WFSSL-RFK(_ _)
12-9 38 in. Shunt with single resistance, Meter, Leads 506WFSS38-(_ _)V
12-8 38 in. Shunt with single resistance, Leads 506WFSS38-(_ _)L


508 Series Power Imbedded Rail Shunts


Adjustment and testing of track circuits that operate in an imbedded, or flush, rail environment are difficult if not impossible with conventional clamp type shunts. Even File or Probe Shunts, while effective for quick tests of such track circuits can be difficult to use for adjustment purposes. S&C Distribution Company offers track shunts equipped with easy-to-use, specialized clamps for use in imbedded track.

Whether the flangeway is created with plastic, rubber, metal, concrete or macadam, the 508 Series Power Imbedded Rail Testing Shunts provide a very effective means of applying firm electrical connections to the rail. Accurate and reliable adjustments to, and testing of, track circuits working in such environments are readily achieved.

Unique design of the connectors and shunt wires assures extremely low probability of resistance variations within the shunt. Switchable between common testing values and zero ohms with test nut. For the large variety of resistance values available, see the Section titled “How To Specify Shunt Resistance”, at the beginning of the Testing Shunts page of this web site. Very close electrical tolerances make these tools highly accurate. Clamps are furnished with handles for portability. Carry Bags are also available.

ORDERING REFERENCES
Reference Description Part Number
1 Zero Ohm, Hardwire Power Shunt 508-00
2 Single Resistance & Zero Power Shunt 508-(_ _)
3 Dual Resistance & Zero Power Shunt 508-(_ _) (_ _)
4 Larger Shunt Carry Bag, HD, zippered 506BZB
Replacement Parts
5 Zero Ohm, Hardwire Power Shunt Wire S-Assy 508-00B-1
6 Single Resistance & HW Shunt Wire S-Assy 508-(_ _)-1
7 Dual Resistance & HW Shunt Wire S-Assy 508-(_ _) (_ _)-1
8 Power Imbed. Rail Shunt Clamp S-Assy 508-25-2
9 Connector, Short Tip, f/Imbed. Clamp, compl 508-25-2-3A
10 Rounded Tip T-Screw f/Imbed. Clamp 508-25-1-1


236-382 Obstruction Gauge

Obstruction Gauges are used to comply with FRA required tests of track switches. They are used to determine if a power operated switch or a hand operated switch and lock movement has been adjusted properly. Proper adjustment is deemed to occur when the switch cannot be locked up when the appropriately sized obstruction is placed between the switch point and stock rail, six inches from the end of the switch point.

The design concept S&C Distribution Company has employed provides four gap gauges of standard values and in combinations that enable fast changes over to values used for different tests. The design also assures more stable, self-retaining mounting to the rail during tests.

Gauge No. 236-382B (Dwg. To the left) offers the gap gauges most common to signal testing (AREMA standard). Gauge No. 236-382A provides a 5/16th inch gap gauge that addresses special adjustment to M-23 Switch Machines where the practice of floating off the lock rods occurs. At locations where a split point derail is operated with a switch machine or a hand operated switch and lock movement, we offer a special gauge, No. 236-382C, where a ½ inch gap gauge is provided.

ORDERING REFERENCES
Description Part Number
Switch Obstruction Gauge with 3/16, ¼, 5/16, and 3/8 Gap Gauges Side 1 with 3/16 & 5/16 in Gaps and Side 2 with ¼ and 3/8 in Gaps 236-382A
Switch Obstruction Gauge with 1/8, 3/16, ¼ and 3/8 in Gap Gauges Side 1 with 1/8 and ¼ in. Gaps and Side 2 with 3/16 and 3/8 in. Gaps 236-382B
Switch Obstruction Gauge with 3/16, ¼, 3/8 and 1/2in. Gap Gauges Side 1 with 3/16 and 3/8in. Gaps and Side 2 with ¼ and 1/2in. Gaps 236-382C
Switch Obstruction Gauge with 1/8, 3/8, ¼ and ½ in. Gap Gauges Side 1 with 1/8 and 3/8in. Gaps and Side 2 with ¼ and 1/2in. Gaps 236-382D

506GR Shunt


Our New Guard Rail Clamp Shunt, with a Guard Rail Clamp on one end as pictured above, is a shunt that we make for applications where track circuits fall in areas, where guard rails are also used. The Clamp is designed to allow the end to which the shunt wire attaches to, fit into the flangeway. The wire connector passes over the guard rail, allowing the shunt wire to cross the track unobstructed, to another Guard Rail Clamp or conventional clamp if another guard rail is not in service. The Guard Rail Shunt is available in two configurations. One with Guard Rail Clamps on both ends, and one with a Guard Rail Clamp on one end, and a conventional clamp on the other.

ORDERING REFERENCES
Description 1 Resistance 2 Resistances
Guard Rail Shunt w/ One Guard Rail Clamp And One Conventional Base-of-Rail Clamp 506GR-( _ _ )B 506GR-( _ _ ) ( _ _ )B
Guard Rail Shunt w/One Guard Rail Clamp And One Conventional Head-of-Rail Clamps 506GR-( _ _ )H 506GR-( _ _ ) ( _ _ )H
Guard Rail Shunt w/ 2 Guard Rail Clamps 506GR2-( _ _ ) 506GR2-( _ _ ) ( _ _ )








506 Series, Five-Resistor Commissioning & Testing Shunt For GCP 4000 ® Island Circuits


Pictured above is the Clamp Bracket version of the 506 Series, 5-Resistor Commissioning and Testing Shunt that provides the five individually selectable resistance values (0.06 Ohm, 0.12 Ohm, 0.30 Ohm, 0.40 Ohm and 0.50 Ohm) intended for use in set-up calibration and sensitivity testing of GCP-4000 ® island circuits.

Set-up is achieved by clamping the shunt with the appropriate (generally established by the railroad engineering office) resistance value, at the receiver feed wires, then activating calibration of the island card.

Once calibration is completed, a 0.06 ohm shunt (also included in the 506 Five Resistor Shunt) is used at the attach points of both transmit and receive sets of wires of the GCP-4000 ® to satisfy the FRA requirement that the circuit will drop out on application of a 0.06 ohm shunt.

In a maintenance application, shunting sensitivity can be determined by clamping the 506 Five Resistor Shunt at the receiver feed wires and changing the resistor settings until the island circuit drops. That value is the shunting sensitivity.

ORDERING REFERENCES
Item No Description Part Number
A Shunt, Clamp Bracket, 5 Resistance; .06,.12,.30,.40,.50, Bag 506CB-612345Z
B Above, but Base of Rail Clamps, Bag 506-612345Z