Direction indicator systems for vehicles

A road vehicle direction indicator system for a vehicle unit, said system comprising two sets of direction indicator lamps for respective sides of the vehicle unit, a selector switch operable to select the operation of one or the other of said sets of lamps, an electromagnetic relay having a pair of contacts connected in series with said selector switch so that when the contacts are closed electric current will be supplied to the selected set of lamps, an oscillator for driving said relay, said oscillator including a capacitor, a charge/discharge circuit for the capacitor, first switch means operable to modify the operation of the charge/discharge circuit, a control input for said first switch means, a reference voltage source, second switch means operable to change the output of the reference voltage source, a control input for said second switch means, and a comparator for comparing the capacitor voltage and the reference voltage, said comparator providing a signal to control the energization of said relay when the capacitor and reference voltages at the inputs of the comparator become substantially equal, said control inputs being electrically connected to said relay contacts so that the operation of the charge/discharge circuit is modified and the output of the reference voltage source changed, only when the relay contacts change their state.