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Controlling & Isolating Sidings

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The MR204 can be used to control the Track Power of a complete Siding System. In the diagram below the first MR204 on the right is controlled by the Points switch for PM1, this in turn is switching ON or OFF the power to the Track to all siding above PM1. So with PM1 in the straight through position the MR204 has removed power from the tracks above IS1. When the Points PM1 are changed to Turn Out power is restored to tracks above IS1. If you are removing a Locomotive from Siding 2, then PM3 Points should be in the Turn Out position switching power OFF to the tracks above IS3. This will allow the Loco to move from Siding 2 to the Main Line. Resetting PM1 to Straight Through will switch OFF Power to all the Sidings. (Note 1)

Start by fitting Isolating Fishplates to all the position shown by an orange line IS1 to IS3. Ensure you have Negative Feed to all the lower tracks of each siding (shown in violet). The positive feed from the Speed Controller goes to Terminal 1 on all the MR204’s. As the drawing above shows there is no power on the tracks above the Main Line. PM1 In the position shown the contact on MR204-1 the wiring must come from the Normally open contact (3) to ensure there is no power onthe Turn Out at IS1 and above.

To remove a Loco from Siding 2, PM1 must be in the Turn Out
position thereby putting power on the Siding Feed Track. PM2
remains the same as the drawing Isolating Siding 1. PM3 is
now put in the Turn Out position giving power to Siding 2 and
isolating everything above it.
This gives a Speed Control path from Siding 2 to the Main Line
with all other sidings are Isolated.

The switch used to activate the points in this case is a
Momentary (centre biased) mini toggle switch, this supplies
a short pulse to the Point Motor and the MR204. The feed for
the Point Motors comes from a separate Power source of a
constant 12 – 16v DC.

The second set of Change over contacts on the MR204 (T2 Terminals
1 -3) can be used for a number of things. A two aspect signal on each
siding. A 2 aspect indication back at the control Panel Isolating the
Negative track in each position. Isolating a second Speed Controller

Note 1:  With PM1 in the Straight Through position, all the Sidings are Isolated, you could therefore have a separate Speed Controller connected to the siding layout so that shunting can be done independently of what is going on elsewhere. However before changing PM1 you need to ensure that the second Speed Controller is Isolated from the Tracks. This can be done by using a second MR204 paralleled to MR204-1, so that both the Positive and Negative Feed of Speed Controller 2 goes through the contacts first before feeding the siding tracks.