NPR 738 Operating powered interlocking machines

Introduction

Powered interlocking machines use electrical relays or computers to interlock points and signals. Interlocking machines check and set the points and signals in a route.

Point indicator lights show that points are:

• able to respond to operation of the point-setting levers, toggles or rotary controls
• set in the intended positions.

Flashing point transit indicator lights show that the relevant points do not have detection, because:

• the points are not in position, or
• facing point locking is not engaged, or
• the points are changing position.

Relay (unit lever) interlocking machines

Unit lever interlocking machines have controls to check and set points and signals individually. Controls are numbered and colour coded:

Steady white indicator lights show that points are in the NORMAL or the REVERSE position.

Steady point lock lights show that the position of the relevant points cannot be changed.

Qualified Worker

1. Set points to:
   1. NORMAL by moving a lever back, a toggle up, or a rotary control left, or
   2. REVERSE by moving a lever forward, a toggle down, or a rotary control right.
2. Check point indicator lights to make sure that points have operated correctly.
3. Set signals to:
   1. STOP by moving a lever back, a toggle to up or middle, or a rotary control to left or middle, or
   2. CLEAR by moving a lever forward, a toggle down or up, or a rotary control right or left.
4. Check signals or signal repeaters to make sure they have operated correctly.

Route-setting interlocking machines

Route-setting interlocking machines check and set a complete route for an intended movement.

The machines:

• check that no conflicting movements have been set already
• set the points and signals for a route.

Route-setting buttons are colour-coded or pattern-coded:

Individual controls can operate points independently of the route-setting. These controls must be:

• kept in the centre position to allow the route-setting function to operate, or
• when an unsignalled movement is to occur, set to NORMAL or REVERSE to lock them in the correct position.

A green FREE indicator light shows that the relevant points are able to be moved.

One Control Switch (OCS) route-setting

The Qualified Worker uses a single button to set a route. A flashing green light in the signal repeater symbol shows that the route is being set. The light steadies when the route is set.

A yellow indicator light in the signal repeater symbol shows that a subsidiary route has been set.

Qualified Worker

1. Press the route button for the intended route.
2. Check that:
   1. a steady green light shows that the route has been set
   2. signals for the route have cleared.
3. Press the relevant CANCEL button to cancel a route.

Entrance-Exit (NX) route-setting

The Qualified Worker sets the start and end of the route.

A white light within the COMMENCE button:

• flashes if the COMMENCE button is pressed
• steadies when the route is set.

A row of steady white route lights on the indicator panel:

• flashes until points in the route have been set
• steadies when the route has been set.

If a train occupies a portion of track in the intended route, the indicator panel lights representing the occupied portion change to red.

Qualified Worker

1. Press the COMMENCE button for the signal at the start of the route.
2. Press the FINISH button for the end of the route.
3. Check that a row of steady white lights shows that the intended route is set.
4. Check that a steady green light in the signal repeater shows that the signal has cleared.
5. Pull out the relevant COMMENCE button to cancel a route.

Failure of intended route to set

Qualified Worker

1. If the route does not set, or if signals do not clear, check that:
   1. the route does not conflict with a route already set
   2. required time releases have operated.
2. Check that you are operating the correct controls in the correct order.
3. Cancel the intended route. If necessary, cancel routes that affect the intended route.
4. Make at least three attempts to set the route.
5. If a set of points does not have detection, check, where practicable, that the points are not obstructed.
6. If the route cannot be set, tell:
   1. a Signals Maintenance Representative
   2. the Network Controller.