SWAMP CREEK & WESTERN
RAILROAD ASSOCIATION

211 Railroad Ave. Edmonds, WA 98020

LAYOUT ELECTRICAL MANUAL

Established December 5, 2000

Revised by page

XI. - HIDDEN TRACK DETECTION CIRCUITS

XI. - HIDDEN TRACK DETECTION CIRCUITS:

Waitsburg loop, Holden loop and the Gorge by-pass are all hidden from view. Circuitron DT-4 Rolling Stock Detector circuits are employed to show track occupancy and train movement within these areas. The DT-4 uses optic sensors and electronic circuitry to light LEDs on the control panels. Each DT-4 contains four independent detection circuits.

The DT-4s operate on 10-18v DC input. A wire connects to each of the four sensor with an independent common return. Another wire connects to each of the corresponding LED indicators on the control panel with a common return.

Waitsburg Loop uses twelve (12) DT-4 units for a total of forty-eight (48) detectors. Holden Loop used one additional DT-4 because of its length for a total of fifty-two (52) detectors. The Gorge by-pass uses three (3) units for a total of twelve (12). Each is wired independently of the other. The loops are wired identically so do not confuse them. Holden is on the bottom and to the west. Waitsburg is on top and to the east. The Gorge spans the middle. While each loop appears only on the local control panel the Gorge appears on both.

A.   Telco Color Code:

As with our hand-held throttle cabling the telephony standard wiring color code is employed to keep the installation neat and orderly.

The center section of each loop is wired with one (1) standard 25 pair (24 ga.) telephone cable. Note however that rather unusually the pairs are split so as to use the wires in groups of five: with four wires for each detector circuit and one for the common return.

The DT-4 units are housed against the south wall below the respective control panels. Cables run from each of the units out to the center of the loops, via a telco "punch-down" distribution block, and then out to each sensor.

As the staging tracks exhaust the 25 pair cable the lead tracks are direct runs back to the DT-4 units.

A corresponding 25 pair cable connects the DT-4s to the LEDs on the panels.

Connectors on these cables allow for the panels to be disconnected and removed for construction and maintenance, off site, if necessary. The lead track LED circuits are run through spares in the Gorge cable. The other components (switch machine control and indications) are also easily disconnected.

! ! ! ! IN NO CASE SHOULD ANY SPARE WIRE BE CUT ! ! ! !

All spare wires are to be pigtailed or dressed for future access should a fault occur or additional circuits become necessary.

The wiring color codes must be strictly observed!

The cables are made up of twisted pairs of the so called "ring" colors: blue, orange, green, brown and slate and their mates, the "tip" colors: white, red, black, yellow and violet. Always in that sequence.

The first wire is solid white (the plastic insulation is white) with a blue stripe painted on. Its mate is a blue wire with a white stripe. They make up the first pair. The second pair is white with an orange stripe and its mate is orange with a white stripe. Once we get through the five ring colors we go back through them but with the next tip color, red. Then black, yellow and violet for all 25 pair.

As mentioned, normally the pairs are kept together in telephony work however, here for our convenience, we will be splitting the pairs and using them in sets of five but we will be using them in the same sequence of tips and rings progressively through the five tip color sets.

So, first we will use all the white wires, then their mates, then the reds with their mates, and so on.

A special telco "punch-down" tool is required for the block connections and is kept in the cabinet. In a pinch, a screw driver and long nose pliers will do but be careful.

B.   LOOPS: 25 pair Telco Cable Split-Pair Wiring Color Code:

TRACK OCCUPANCY DETECTORS - DISTRIBUTION CABLE DESIGNATIONS

COM. - common return

C.   GORGE: 25 pair Telco Cable Split-Pair Wiring Color Code:

TRACK OCCUPANCY DETECTORS - DISTRIBUTION CABLE DESIGNATIONS

COM. - common return

HK refers to K in Holden, HL refers to L in same, WK refers to K in Waitsburg and so on...

D.   Optic Sensors:

The optic sensors are strategically spaced throughout the loops.

The staging tracks are each electrically isolated dividing them into two equal lengths of approximately 10 feet. Train travel in all cases is in a counter-clockwise direction. Each staging section has six (6) detectors.

Trains being stages should be stopped shy of the nose detector which indicates the fowling point and beyond the tail detector.

The sensors are mounted between the tracks through a 5/32" hole. This size hole will allow the wires to pass but not the sensor. They are very small and fragile. The leads are soldered to feeder wires and shrink wrapped. They are fed through the hole and the wires are bent at 90 degrees and carefully secured and dressed so as not to dangle nor allow the sensor to protrude.

Again, each set of four sensors is connected to the common return on one side and the first four wires sequentially as has been described in the 25 pair telco cable on the other. These wires run back to the central distribution block where they are punched down in the proper position. Note that the block is split pairs in the order as has been described.

The other side of the cable runs directly back to the DT-4 units and is hard wired there.

E.   LED Panel Indicators:

The LEDs are connected on one side to the common (+) v DC power supply. The other side is connected to the respective DT-4 circuit via another 25 pair telco cable with a matching color code. So, just as sensor A-1 is connected with the white/blue wire its matching LED is also connected with the white/blue wire.

The 25 pair cable is connectorized between the panel and bench work. The male and female cable ends should snap together snugly. There are small screws at the tip of each end that secures them. Release these to disengage.

The other end of the cable is hard wired to the DT-4 units.

The LED connections for the Gorge appear on both Waitsburg and Holden panels. These are tied together via another 25 pair cable. As mentioned earlier, the staging tracks exhaust all the first 25 pair cable so the lead track detectors designated HK 1-4, HL 1-4, HM 1-4 for Holden and WK 1-4, WL 1-4 for Waitsburg employ this second cable.

Spares:

Note that the spares on the connectorized cables going to the control panels are used for auxliary LED connections (turnout position, turnout lock out, and remote override indications).

A.   PANELS: 25 pair Telco Cable Split-Pair Wiring Color Code:

COM. - common return

A.   Sensor Light Source:

When light is stopped from hitting the optical sensors, such as a train passing over, the DT-4 circuit causes the occupancy indicator LED on the control panel to light up. Because of the lack of light in the hidden track areas we must supply them with some.

12 volt lamps are placed strategically throughout the runs. They are fed by an 18 ga. BLACK and WHITE supply buss. The power supply for these is housed underneath Rimrock.

H.   Notation on Neatness and Style:

We have tried to install the units and their cabling with care and forethought. We would like to urge those that follow to do the same. Be careful when you remove sheathing, don't nick the wire. Allow for the right amount of slack and dress the cabled neatly. Follow the color code! We will all be rewarded with reliable service through your due care.

SWAMP CREEK & WESTERN
RAILROAD ASSOCIATION

211 Railroad Ave. Edmonds, WA 98020