Call change ringing is a branch of the art of change ringing, in which a group of English-style full-circle bell ringers are instructed continually to create different sequences, or changes, of the bells' striking order. Each command from the leader or "conductor" of the ringing results in a new sequence of sounding the bells. Each sequence is repeated until the next command or "call". The technique was probably developed in the early 17th century in the early days of change ringing.