Multiple Signals Example

Lets use the Signal Manager to define multiple signals on two nodes.

Here is a portion of a track plan for a larger layout:

Nodes 4 and 5 are physically adjacent and share track between them. We’ll be programming signals for the Main line; diverging tracks are for sidings, team tracks or a small yard.

Before configuring signals, nodes 04 and 05 have to be configured to selectively listen for each other’s objects (See Blocks and Turnouts), as shown below:

Node 04 Blocks & Turnouts #

Node 5 Blocks & Turnouts #

Signal S0 on Node 04 #

This signal faces east and controls west-bound traffic on the mainline from Node 04, Turnout 0 to Node 05, Turnout 4. Here is one way to configure the signal:

In this case, the state of the signal depends on local block 0 and local turnout 0, plus two blocks and two turnouts on adjacent node 05 that this node monitors. Further, not all conditions require a STOP aspect; two remote conditions are deemed far enough away to justify APPROACH instead.

When interpreting these settings, keep two automatic rules in mind:

• CLEAR or OFF are defined as “no other defined condition tests true”; and
• STOP conditions always take priority over APPROACH, which always takes priority over CLEAR/OFF.

So, the rule for S0, Node 04, would look like this written out:

IF BLOCK 0 IS OCCUPIED OR
  BLOCK 9 is OCCUPIED OR
  TURNOUT O IS NOT ALIGNED MAIN OR
  TURNOUT 9 IS NOT ALIGNED MAIN
THEN SET ASPECT TO STOP
ELSE IF BLOCK 8 IS OCCUPIED OR
  TURNOUT 8 IS MOVING
THEN SET ASPECT TO APPROACH
ELSE SET ASPECT TO CLEAR

S1 on Node 04 #

S1 faces west protects Turnout 0 only, so here we’re creating a STOP/OFF signal. You would likely use additional signals in this area to convey additional information beyond the turnout.

The resulting rule:

IF TURNOUT 0 IS MOVING
THEN SET ASPECT TO STOP
ELSE SET ASPECT TO OFF

S0 on Node 05 #

This signal faces west and controls east-bound traffic from Node 05, Turnout 4 to Node 04, turnout 0.

The resulting rule:

IF BLOCK 3 IS OCCUPIED
  OR BLOCK 4 IS OCCUPIED
  OR TURNOUT 4 IS NOT ALIGNED MAIN
  OR TURNOUT 5 IS MOVING
THEN SET ASPECT TO STOP
ELSE IF TURNOUT 8 IS MOVING
THEN SET ASPECT TO APPROACH
ELSE SET ASPECT TO CLEAR

S1 on Node 05 #

This signal faces east and controls east-bound traffic through the interchange from Turnout 5 through Turnout 4 to Block 2. We want to the signal to warn if Turnout 4 is lined for the divergent route since that leads to team tracks or if Block 2 is occupied. For both conditions we want S1 to show APPROACH.

The resulting rule:

IF BLOCK 3 IS OCCUPIED
  OR TURNOUT 5 IS NOT ALIGNED MAIN
THEN SET ASPECT TO STOP
ELSE IF BLOCK 2 IS OCCUPIED
  OR TURNOUT 4 IS NOT ALIGNED MAIN
THEN SET ASPECT TO APPROACH
ELSE SET ASPECT TO CLEAR

In this situation, you could set the aspect if Block 2 is occupied to STOP. However, because STOP conditions take priority, any occupancy of Block 2 would force STOP at S1 even when Turnout 4 is lined for the divergent route. Instead, the best approach in a situation like this is to limit S1’s primary responsibility to the T5 -> T4 section, and assume an additional downstream signal to fully cover Block 2.

Of course, using multiple signal heads (each head is a logical signal) is another way to handle complex intersections.