<P> Bell codes or Buzzer codes (US Communication Signal Appliance codes) are a series of bells or buzzers used on passenger trains for communication between the driver and guard . </P> <Table> <Tr> <Th> Signal </Th> <Th> Meaning in Great Britain </Th> <Th> Meaning in India </Th> </Tr> <Tr> <Td> </Td> <Td> Stop </Td> <Td> Stop train </Td> </Tr> <Tr> <Td> 1--1 </Td> <Td> </Td> <Td> Zone of speed restriction over, resume prescribed speed </Td> </Tr> <Tr> <Td> 1--2 </Td> <Td> Close doors </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> Ready to start </Td> <Td> Start train </Td> </Tr> <Tr> <Td> 2--2 </Td> <Td> Do not open doors </Td> <Td> Passing automatic signal at' on' </Td> </Tr> <Tr> <Td> </Td> <Td> Set Back </Td> <Td> Guard required by driver </Td> </Tr> <Tr> <Td> 3--1 </Td> <Td> Lock central door locking </Td> <Td> </Td> </Tr> <Tr> <Td> 3--2--1 </Td> <Td> Testing doors </Td> <Td> </Td> </Tr> <Tr> <Td> 3--3 </Td> <Td> Guard required by driver, or guard or driver to speak on the telephone </Td> <Td> Guard's warning when the motorman exceeds the speed prescribed </Td> </Tr> <Tr> <Td> 3--3--1 </Td> <Td> Release central door locking </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> Slow down </Td> <Td> Protect train in rear </Td> </Tr> <Tr> <Td> </Td> <Td> Driver / Guard leaving the train </Td> <Td> </Td> </Tr> <Tr> <Td> 6 </Td> <Td> Draw forward </Td> <Td> </Td> </Tr> <Tr> <Td> 9 </Td> <Td> Police assistance required </Td> <Td> </Td> </Tr> </Table>

What is the bell on a train for