Blinker light control unit

Claim 1

In a pulse generator unit having an input for connection to a voltage source and an output for connection to a selected group of parallel connected loads for applying periodic electrical current pulses to the selected group of parallel-connected loads, the pulse generator unit including: an oscillator stage connected between the input and the output for producing an output signal oscillating cyclically between a value corresponding to an active fractional period during which an operating current pulse is delivered to the loads and a value corresponding to an inactive fractional period during which the loads do not receive sufficient current to operate; impedance means connected between the input and the output; switching means controlled by the output signal from said oscillator stage and operatively connected to said impedance means for causing said impedance means to have a low impedance value which creates a current flow to place said loads into operation during each active fractional period, and to have a high impedance value which creates a current whose amplitude is less than that required to place the loads into operation during each inactive fractional period, the current flow during each inactive fractional period producing, across the loads, a voltage drop having a predetermined value when all of the loads of the selected group are operative and a higher value when at least one of the loads is inoperative; and an indicator stage connected to the output for monitoring the voltage across the loads and producing an indication representative of the value of that voltage, the improvement wherein: said oscillator stage includes only a single capacitor connected for determining the duration of both the active and inactive fractional periods, and said indicator stage includes: voltage responsive switch means having a control input connected to the output of said unit to receive the voltage across the loads, which voltage places said switch means in an operative switching state during an inactive fractional period only when the voltage across the loads is greater than said predetermined value; and a voltage divider having one end connected to said switch means, with an intermediate point of said voltage divider being connected to one side of said capacitor, said switch means and voltage divider being connected together for varying the maximum voltage to which said capacitor charges during each inactive fractional period by an amount proportional to the voltage division ratio of said voltage divider only when said switch is in its operative switching state, so as to vary the repetition frequency of the output of said oscillator stage when an inoperative load is present.