Railway block code
The railway block signalling bell code is a system of bell rings used in Great Britain to communicate between manually operated Signal Boxes. Each signal box would have a bell circuit to the box on either side of it along the line. The equipment would consist of a plunger or tapper which if pressed, rings the bell in the neighbouring box. The neighbouring box would have a key for communicating back, therefore each box has a key which rings the bell in the other box. Where a signal box communicates with more than one other box, each bell would have a different tone, so that the signalman could tell them apart by ear.
Examples
Although codes varied from region to region, the following shows a few selected standard UK bell codes:Code | Meaning |
1 bell | Call attention |
2 bells | Train entering section |
2 - 3 bells | Is line clear for light engine? |
2 - 2 - 1 | Is line clear for empty coaching stock train? |
3 | Is line clear for stopping freight train? |
3 - 1 | Is line clear for stopping passenger train? |
3 - 1 - 1 | Is line clear for express freight train? |
4 | Is line clear for express passenger train? |
4 - 1 | Is line clear for mineral or empty wagon train? |
2 - 1 | Train arrived |
3 - 3 | Blocking back outside home signal |
5 - 2 | Release token |
2 - 5 | Token replaced |
5 - 5 - 5 | Opening signal box |
7 - 5 - 5 | Closing signal box |
6 | Obstruction danger |
4 - 5 - 5 | Train running away on Right Line |
2 - 5 - 5 | Train running away on Wrong Line |
16 | Testing bells and instruments |
Typical use
These would be used as follows between two signal boxes A and B. Assume a train is to pass from the block controlled by A to the block controlled by B. This must be agreed and permitted by the signalman in box B. Here is the sequence of bell codes and associated actions:- Box A sends 1 bell to box B.
- Box B replies with 1 bell to box A.
- Box A sends 4 bells to box B.
- Box B sends 4 bells to box A.
- Box A sends 2 bells to box B. This is sent as the train passes box A and enters the block controlled by B.
- Box B sends 2 - 1 bells to box A.