GB1369442A - Vehicles having fault indicating systems - Google Patents

Abstract

1369442 Fault-indicating systems JOSEPH LUCAS (INDUSTRIES) Ltd 6 Dec 1971 [22 Dec 1970] 60745/70 Heading G4H In a fault indicating system the operational condition of a plurality of D.C.-operated devices 12, 12a, is determined during an interrogation cycle comprising a transmission period in which an oscillator 18 in a monitoring unit 18-21 sends an address signal to fault indicating circuits 23-27 connected to each device 12, and a plurality of receiving periods during each of which a respective circuit sends back to the unit a reporting signal whose position within its respective period is indicative of the operating condition of the corresponding device. Receipt by the unit of a signal in the first or second half of its receiving period respectively indicates satisfactory operation of the device or the need for attention, and the absence of a signal in both halves indicates failure of the device; alternatively, a two-state signal may be used to indi cate whether or not the device is functioning. The address signal is a pulse train of predetermined frequency and length; on receipt of this signal a detector 23 activates an answer unit 26 via delay unit 24 which introduces a delay representative of the device. The output signal from 26 is fed through unit 24 again and is subject to a further delay which is determined by a condition monitoring unit 27 connected to the device 12; this doubly delayed signal is fed to a detector 19 in unit 18-21 and is used by a correlator 20 to activate display and warning devices 21. In one embodiment, 26 is a gate which is opened after the count-down of a counter 24 from a value which is indicative of the device 12 and of its operating condition, the opening of the gate allowing a pulse train from an oscillator 25 to be fed to detector 19: here gates (one for each device) are sequentially enabled (at the beginning of each receiving period), the delay before the arrival of the respective pulse train providing the required information about the condition of the device.