Patent GB-1388988-A (GB)
Title: Vehicle multiplex circuit having function priority
IPC: B60R25/04
Filed: 1973-10-04
Abstract: 1388988 Electric selective signalling GENERAL MOTORS-CORP 4 Oct 1973 [13 Oct 1972] 46314/73 Heading G4H In a vehicle multiplex system, a plurality of electrically-operated circuits are operated in response to coexistence of a control signal with a time slot respective to the circuit, the control signal being produced in response to an intermediate signal produced in response to a manual switch respective to the circuit, the circuits being divided into two groups, there being means for extending the time slot of a circuit of the second group in response to the intermediate signal, and a priority circuit for disabling the intermediate signal in the case of a circuit of the second group when one of the switches for the first group is operated whereby the circuits of the first group can be operated in response to their switches while one of the switches for the second group is operated. As disclosed, a vehicle has 6 circuits controlling right and left front and rear turning lights and right and left windows respectively, there being two bi-stables for each circuit, the 12 bi-stables being connected in a loop with a bi-stable 84 in a control centre 36 shown in Fig. 2, via leads 74, 76, 68, 64. Other leads extending round the loop are a power supply lead 70 for the bi-stables and circuits, a control signal lead 72, a lead 62 for resetting the bistables, and a clock pulse lead 66. The clock pulses on lead 66 come via a NAND 80 from an oscillator 78 and cause the bi-stables in the loop to be set in turn, to define two time slots for each circuit to be used for switching on and off respectively in the case of a light control circuit, and to be used for winding up and down respectively in the case of a window control circuit. The clock pulses from NAND 80 also drive a binary counter 82 decoded at 86. When the left lights or right lights are to be turned on or off, a respective one of four manual switches 88, 104, 116, 126 is closed momentarily. These trigger single-shots 92, 108, 120, 130 so that at each appropriate time slot a bi-stable 94 is set in response to the decoder 86 enabling NANDs 98, 112, 124, 134. The set bi-stable produces a control signal on lead 72 via a transistor 144 and blocks the clock pulses at NAND 80. The bistable 94 is reset and time-slot sequencing continues after a delay defined by a counter 170 (this might be dispensed with). A light control circuit responds to arrival of the control signal on lead 72 to set an SCR if the set input of its first bi-stable is up and the set output of this bi-stable is down, and to reset the SCR if the same is true of its second bi-stable. While the SCR is in the set state the light flashes. When the right or left window is to be wound up or down, a respective one of four manual switches 148, 156, 160, 164 is held down to cause an AND 168 to pass pulses from the oscillator 78 to continually trigger a single shot 100 which is thus kept continuously in the set state so that, via an EXCEL-OR 140, it produces the control signal on lead 72 and blocks the clock pulses at NAND 80. A window control circuit responds to the presence of the control signal on lead 72 to wind its window up or down if its first or second bi-stable, respectively, has its set input up and its set output down. Driving of the window ceases at the end of the control signal which occurs in response to release of the manual switch 148, 156, 160, 164 after which time-slot sequencing proceeds. Operation of any of the light switches 88, 104, 116, 126 while a window is being controlled will cause resetting of the single-shot 100 via diodes 102, 114, 125, 136 so that window control is interrupted and time-slot sequencing continues to deal with the light control. Control of headlamps, reversing lamps, radio, windshield wipers &c. is also mentioned.