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Diamond crossing protector


The Diamond Crossing Protector prevents collisions between two trains meeting on a diamond crossing.

When the diamond crossing Protector detects a train on the main line about to cross the diamond it sets the branch line signals to red and isolates short stretches of track on the branchline before and after the diamond. If a train is approaching on the branchline at the same time then it will stop on the isolated track.


Train detectors TD1 and TD2 are on the main line, the signals and isolation section are on the branchline. When a train crosses TD1 or TD2 the branchline will be isolated and its signals will change to red. Note that if a branchline train has crossed the first isolation section and is on the second then it will be stopped on the diamond crossing. The second diagram shows how diodes are used so that the train is stopped on the isolation section before the crossing but will not be stopped by the isolation section after the crossing. (unfortunately diodes do not work with feedback controllers). The second diagram also shows the location of detectors for a double track mainline.  If the train always runs along the branchline in the same direction only one isolation section (before the diamond is necessary. TD1 TD2 etc need to be a sufficent distance from the diamond to allow time for a branchline train already on the diamond to clear it.

diamond crossing


For a 12 volt DC supply connect the supply positive to the "+" and supply negative to the "o" terminals of the diamond crossing isolator. The IRDOT-1s are wired to the same power supply as shown in the diagram.  Connect the terminal 1s to positive and the terminal 6s to negative.  The units may also be powered from 12 to 16 volts AC. If this is used be very careful to ensure that all terminal 6's of the IRDOTs and terminal "0" are connected to one of the AC terminals and that all terminal 1's and terminal "+" connect to the other terminal of the AC supply. Mistakes in AC wiring can result in damage to the terminal 2 transistor of the IRDOT. To safeguard against damage a diode can be used in one of the feeds from the power supply. 


For a single line crossing one detector is required at either side of the crossing. Wire from terminal 2 one of the IRDOT to terminal D1 of the diamond crossing isolator. Wire from terminal 2 of the other IRDOT to D2". Reed switches can be used instead of IRDOT-1 train detectors.  Wire one end of each reed switch to the "o" terminal. .  Wire the other end of the reed switch as described for terminal 2 of the IRDOT. For double track two more detectors or reed switches are wired to terminals D3 and D4.


diamond crossing detector wired to 2 aspect colour light signals

The Diamond Crossing Protector operates 2 signals either side of the isolation section. The signals must be common negative LED signals. The wiring diagram is shown below.  Resistors are built into the Diamond Crossing Detector so any supplied with the signals are not used.