The Two Crossover Loops with Passing Loop automated track plan adds two track switches and a "passing" loop to the Two Crossover Loops layout. The passing loop allows the order of trains to change, providing more variety of action.

The example layout has fifteen track blocks. Trains move clockwise, in the direction shown by the arrows.

The layout will run three or four trains quite nicely. This layout fully demonstrates an "automated" layout, with the TBC selecting and dispatching trains through the track switches. Fascinating to watch.

This layout is powered with three train transformer circuits. Transformer circuits are required to power multiple trains at once.

The fully automated layout is implemented with ten "Train Block Controllers:" four in "One Block with Power Passing" configuration, three in "Two Track Blocks" configuration, one in "Crossover" configuration, one in "Automatic One-to-Two Track Switch" configuration, and one in "Two-to-One Track Switch" configuration.

Each of the ten track blocks is assigned to "Block One" or "Block Two" for the TBCs. Following shows assignments for each track block.

The isolated outside-rail for each track block is connected to the outside-rail input of its assigned TBC.

The isolated outside-rails of crossover leading and trailing track blocks (L1/T1 and L7/T7) are connected together and one wire connected to the controller outside-rail input for each. (One wire from L1/T1 to the controller and one wire from L7/T7 to the controller.)

Outside-Rails of track switch trailing blocks (T16, T17, T18) have separate connections to TBC outside-rail input terminals. (Unlike the track crossover, outside-rails of leading and trailing blocks of track switches are NOT connected together.)

The isolated center-rail for each track block is connected to the power relay of its assigned TBC.

Crossover leading track blocks are connected to the power relay, but corresponding trailing tracks are not connected to the power relay. Trailing blocks are always powered, with connections shown in a later table.

Center-rails of leading blocks of the "Two-to-One Track Switch" (L15, L3) are connected to separate power relays. The center- rail of the trailing block (T16) is always powered, with the connection shown in a later table.

Center-rails of leading and trailing blocks and the switch of the "Automatic One-to-Two Track Switch" (L4, T17, T18) are connected together and to one power relay. Steel pins are used for all center-rail connections between connected track blocks and the switch.

The assigned train/center-rail transformer post is connected to the power select relay for track blocks controlled by TBCs in "One Block with Power Passing" configuration and to the power relay for blocks controlled by TBCs in "Two Track Blocks", "Crossover", "Automatic One-to-Two Track Switch", and "Two-to-One Track Switch" configurations.

For TBCs in "One Block with Power Passing" configuration, train power from the "FOLLOWING" track block is connected to the select relay and the "select" relay is connected to the train power relay for the track block.

Both track switches are of the O-22 style, with a non-derailing feature and with a built-in electrical switch that interrupts switch power when a switching movement is complete.

The L15/L3/T16 track switch requires no connections to the switch motor.

The L4/T17/T18 track switch is controlled by a TBC relay, with connections shown in the following table.

Additional TBCs in Switch Auxiliary configuration can be used to operate other track switch types.

The center-rail of trailing track blocks (T1 and T7) and the crossover are always powered. These track elements are connected to the power source that is powering the crossover leading track blocks. The crossover track section is powered by steel center-rail pins to the trailing track block sections, or by a wire connected to the crossover center-rail, or both.

The center-rail of the "Two-to-One Track Switch" trailing track block (T16) and the track switch are always powered with the power source that is powering the leading track blocks. The track switch is powered by a steel center-rail pins to the trailing track block.

A given "Train Block Controller" communicates with adjacent track blocks to know if a train arriving in a track block can be powered. Track blocks adjacent to a given controller are designated "PREVIOUS" and "FOLLOWING," relative to train direction. For a given track block, a train has passed the "PREVIOUS" block, and proceeds to the "FOLLOWING" block. In the diagram, block 1 is "PREVIOUS" to block 2 and block 3 is block 2's "FOLLOWING" block.

Each controller block employs two signals for controlling trains in track blocks. Train-In-Block (TIB) is set when a train is in the controlled track block. Train-In-Following-Block (TIFB) is examined to determine if a following block is clear and a train can proceed. For each block, TIB is connected to TIFB of the controller for its "PREVIOUS" block. TIFB for a block is connected to TIB of its "FOLLOWING" block.

The "Two-to-One Track Switch" controller receives one TIFB signal and produces a TIB signal for blocks "PREVIOUS" to each leading track block.

The "Automatic One-to-Two Track Switch" controller receives a TIFB signal from each block "FOLLOWING" the trailing blocks and produces one TIB signal for the block "PREVIOUS" to the leading block.

TBC controller interconnections are listed in the following table.