Robert Boschgmbh

Rainer Rudolph

Jurgen Brauninger

To permit connecting a display characterizing a malfunction, for example malfunction in an automotive vehicle, or another monitored apparatus, and a warning lamp to alert an operator that a malfunction is being indicated to a single connecting line (SL), a coded representation characterizing the malfunction in the form of short pulses (I; 1, 2) is transmitted on the same line, with pulses which are so short that the response inertia of the warning lamp does not perceptively change its brightness (or darkness) level, as controlled by the operating voltage of the warning lamp between a high and a low value. The coded pulse representation is decoded in a microprocessor (MP) and displayed on a display (A) forming part of an evaluation device, coupled to the same single communication line (SL) which may be a single wire with chassis or ground return, or a two-wire connection. Typically, the warning lamp may operate in one to several second intervals (for example flashing), the pulses having pulse duration in the millisecond or fractional millisecond range. The pulses, when the warning signal lamp voltage level is 'high' then are formed by 'low' value pulses, and, if the lamp is dark, so that the operating signal is 'low', the pulses are 'high' and of insufficient duration to cause lighting of the lamp filament.

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Leonberg, Germany

Rainer Rudolph