IR's bell code has some points of correspondence with systems used in the UK in the early part of the 20th century. The system of bell codes to convey messages from one signal box to another is given below. An 'X' indicates a short strike on the bell, and a dash indicates a pause.
Bell Codes Message
Line Clear Inquiry
Train entering Block Section
Train leaving Block Section, Obstruction removed
Cancel previous, Cancel last (given in error)
Danger or Obstruction
Stop and Examine Train
Train passed without tail lamp or missing tail board
Runaway Vehicle (single line, or double line wrong direction)
Runaway Vehicle (double line, right direction)
XXXXXXXXXXXXXXXX (16 beats)
The acknowledgement for each of these messages is given by repeating the same message immediately.