IRDASC SIGNAL CONTROLLERS
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The IRDASCs are infrared train detectors and automatic 2 aspect signal controllers combined on one circuit board.  The Infrared detector works in the same way as the IRDOT.
There are three versions of the IRDASC.  IRDASC-1 is for operating LED signals, IRDASC-2 switches the signal with relay contacts; these contacts can operate bulb or LED signals.  IRDASC-3 has a double pole relay for operating both the signal and isolating the track in front of the signal.
HOW THE IRDASC OPERATES:

There is a train detector (IRDOT-1 for example) at A, an IRDASC at B wired to signal 1 and an IRDASC at C wired to signal 2. The signals are initially at red.  The detector at A will first detect a train travelling from the left.  A wire connecting A to B will tell the IRDASC at B that the train is entering the block section. This causes Signal 1 to change to clear.  After the train passes signal 1 it reaches the IRDASC at B.  When the IRDASC at B detects the train it sets signal 1 back to red.  Simultaneously it will "tell" the IRDASC at C via a wire that a train is entering its block section.  This makes the IRDASC at C set its signal to green.  When the IRDASC at C detects the train it returns signal 2 to red.
This chain of signals can be extended indefinitely.  Each additional signal will use an extra IRDASC to control it.  When signalling an oval, wire the first and last IRDASC together and omit the train detector at A. If the first signal is a starter signal a push button switch can be used to set the signal to clear when the train is due to depart.  The IRDASCs can be used to form block sections.  When used in this  way the signals only change to green for approaching trains when the next block section is clear.
INSTALLATION: Each IRDASC is positioned past the signal where the train is required to return the signal to red.  The IRDASC is fitted beneath the baseboard in the same way as the IRDOT.  It is supplied fitted with a "train detected" LED so the correct operation of the infrared train detector can be checked.  All three types of IRDASC can be used together.  Follow the link at the top of the page if you wish to see the terminal arrangements for the IRDASCs:
WIRING IRDASC-1 TO THE SIGNAL: The IRDASC-1 is supplied with built in current limiting resistors required for the signals LEDs.  If a resistor is supplied with the signal it is not needed.  The left hand diagram shows the usual connection to an LED signal with the LEDs commoned to negative.  The right hand diagram shows how to wire an LED signal using only two wires.
                     
WIRING IRDASC-2 TO THE SIGNAL: The IRDASC-2 uses built in relay contacts to switch the signals. These are shown by blue lines in the diagram.  Wiring the signal is therefore identical to using a changeover switch.  The signal may be powered by either the same supply used for the IRDASC or a separate power supply.  The relay contacts are rated for 2 amps. 
 
The diagram shows the signal wired to use the same supply as the IRDASC.  Wiring to the relay contacts is shown. It is identical to wiring to a changeover switch.
WIRING IRDASC-3 TO THE SIGNAL: The IRDASC-3 uses a double pole relay for connections to the track and signals.  This allows electrical isolation between track, signals and the IRDASCs power supply.  The relays will switch up to three amps. 
The diagram shows the arrangement for using a separate supply for the signal.  The signal could also be powered from the same supply as previously shown for the IRDASC-2.  Note how the internal relay connects both 2 and 4 or 2 and 5 to light the correct bulb.  If a resistor is wired into the supply LED signals can be used.
TRAIN ENTERING SECTION TERMINAL (TES) Activating this terminal "tells" the IRDASC that a train is approaching.  It causes the signal to change to green.  The "train entering section" terminal is usually wired from the "train detected" terminal of the previous IRDASC.  It can also be operated by terminal 2 of an IRDOT-1, a reed switch or a normally open push button switch.  The push button switch is useful for a starter signal.  It is pressed when the train is due to depart.
After passing the signal, the train will reach the IRDASC.  The IRDASC returns the signal to red when it detects the train.  Whilst the train is detected the IRDASC operates the "train detected" terminal.  This terminal can be wired to the "train entering section" terminal of the next IRDASC.  This sets the next signal to green.
SUMMARY OF WIRING: To make the signal change to green as a train approaches and return to red as it passes the following connections are made.  Two wires to power the IRDASC.  Three wires to the signal.  One wire to the "train entering section terminal from the previous IRDASC, (or from an IRDOT-1, a reed switch or a push button switch).  Using the remainder of the terminals to provide more advanced operation is optional.
Diagrams of IRDASC Terminals  
Extra features of IRDASCs

SPECIFICATION
Voltage 12 to 16 volts, AC or DC

SIZE
  Inches Millimetres
Length x Width 4.8 x 1.2 123 x 31
Height of infrared components 0.9 22