GB1351397A - Flasher units for motor vehicles - Google Patents

Abstract

1351397 Lamp failure alarms; road traffic signals on vehicles ROBERT BOSCH GmbH 28 Nov 1972 [29 Nov 1971] 54861/72 Headings G4N and G4Q A flasher circuit for a vehicle comprises: means 40, 41 for varying the resistance of a circuit containing at least one flasher lamp 37, in dependence on the position of a switch 54 which operates the vehicle headlights 52, 53; a pair of control elements, e.g. resistors 55, 56 having a junction 57 which is connected to a switch 59 controlled in dependence on the position of switch 54; and a further switch, e.g. transistor 48 controlled by the control elements and connected to a pilot lamp 51. With headlight switch 54 open, switches 41, 43 are closed shorting resistors 40, 42 and rear turn indicator lamps 37, 39 operate at full brightness when actuated. Switch 59 is also closed, shorting resistor 56, the full lamp current flowing through resistor 55, whenever flasher switch 44 closes, being sufficient to turn on transistor 48 and energize pilot lamp 51. If one of the turn indicator lamps 36 ... 39 fails, the current through resistor 55 is insufficient to turn transistor 48 on, and pilot lamp 51 remains unlit. When switch 54 is closed, switches 41, 43 open to reduce the brightness of the rear turn indicator lamps 37, 39, and thus reducing the current through resistor 55. In order to ensure a sufficient base-emitter voltage to turn on transistor 48, switch 59 opens to switch a further resistor 56 in series with resistor 55. In a modification, Fig. 2 (not shown) the two resistors 55, 56 and transistor 48 are replaced by a relay having two windings, so that the number of turns is increased in the low current condition.