Lever Frames

Once upon a time trains were controlled by men with flags ….

but this was a bit restrictive so, the signal box was invented, whereby one man could control points and signals over a number of tracks and a wider area.

From Build 100, Rail3D now has the facility to model traditional lever frame signal boxes and put you in control of the levers.

Features of a Lever Frame box

The Levers

First and foremost, the levers: The levers control the points and signals.

  • Red levers control signals. When the lever is at the back of the frame (in the frame), the signal is at danger (“on”). When the lever is pulled, the signal is cleared.
  • Yellow levers control distant signals.
  • Black levers control points. When the lever is in the frame, the point is set for its normal route, when the lever is pulled, the point is reversed.
  • Blue levers control Facing Point LocksFacing Point Locks. (fpls). These are a safety device, such that when the lever is pulled the relevant point is locked to prevent it moving when a train passes over the point.

The levers are interlocked this is a system of mechanical locks and bolts (and some electrical) that prevent levers being moved into dangerous configurations. For example,

here, it would be dangerous to pull signal 41 if the points were set for the crossover, so the interlocking would prevent this.

Track Diagram

The track diagram shows the area controlled by the signal box, points and signals are numbered with the number of the corresponding lever (This is important in order to know which lever to pull!).

Depending on the age and type of the signal box, there may be track circuit lamps on the diagam as well - these light up when a section of track is occupied and help the signalman to know where the trains are.

Block Instruments

The block instruments are used to communicate with the signalboxes either side in order to get permission to send trains and grant permission for trains to approach. Communication is done by a series of bell codes.

Block instruments come in a wide variety of types: at the moment Rail3D implements a simplified form of instrument and only uses a simple subset of bell codes.

The Register

The train register is used to record train movements and other key activties in the box. It is a vital record of what is going on and in busy box it is essential in order to keep track of the state of play.

A full size register has a lot of information on it:

Photo: Alan Perryman

At present Rail3D implements a simplified form of the register:

The register has two “pages”: one for down trains on the left and one for up trains on the right. Each “page” is divided into two, with the times of trains approaching the box on the left-hand half and the times of trains going away from the box on the right.

See also: