Device for measuring motion parameters of a bicycle

The sensor consists of a rectangular compartment (29) which contains a round lozenge (28) able to open and close a reed relay (26) at each turn of the compartment. Circuits (34-38) measure the average speed of the sensor signal over a chosen time and convert it to digital form for radio transmission (44) to a receiver (46) and indicator (14). There are circuits (58,60,62) which control the time period and the optimum transmission instant. An Independent claim is also included for a bicycle which uses the sensor/transmitter mounted on a wheel or crank sprocket.