bells in Canterbury during Chaucer's time?

[Laura Dickerson]

  The current tower at the cathedral is from 1500.  I found a reference 
to a clock tower there in 1292.  Mechanical clock?  Were there some sort 
of chiming hammers attached to a clock
mechanism that early, or would people have been ringing the bell(s) 
based on the clock time? 
Any information would be appreciated.
Laura Dickerson