Abstract: A vehicle monitoring system is described having an arrangement installed within a vehicle, wherein the system includes an external data terminal for communicating information to a remotely located base station. The arrangement includes a plurality of communication modules, each being capable of communicating messages associated with performance of the vehicle; a data bus member for electrically intercoupling the plurality of communication modules and for receiving the communicated messages therefrom; a driver interface module for transmitting messages to and for receiving messages from a vehicle operator; and a recorder coupled to the data bus member for recording information associated with performance of the vehicle which has been transmitted over the data bus member by the plurality of communication modules, coupled to the driver interface module via a second data bus member for transferring messages therebetween.

Abstract: A meter drive inhibit circuit is provided whereby an erroneous jump of the meter pointer upon system power-up or subsequent microcomputer reset operation is inhibited. A pulse generator is utilized to produce output pulses relating to the rate of rotation of a drive shaft in a typical tachometer application. Such output pulses are provided to a meter drive circuit which in turn provides an output to an electromechanical meter. Such electromechanical meter will display an output related to the time average value of pulses input to the meter drive circuit. An inhibit circuit stage is connected to the meter drive. A microcomputer is utilized to sense the power-up condition of the meter circuit and activate the inhibit stage. When activated, the inhibit stage will prohibit the meter drive from providing an output to the meter and thereby prevent the erroneous jump of the meter pointer upon system power-up.

Abstract: A meter overdrive protection circuit is provided using a variable duty cycle drive pulse. Such meters usually comprise speedometers and tachometers used in highway vehicles such as trucks. A programmable pulse generator is utilized to provide a series of pulses of a selected width depending on the truck model. A sensor input corresponding to the rate of rotation of the drive shaft of the truck is used to trigger the pulse generator to produce each output pulse. Such output pulses are supplied to a meter drive which, based on the time average value of the output pulses received, displays an output value related to the rate of rotation of the truck drive shaft. Upon the triggering inputs exceeding a preselected frequency, a microcomputer will change the pulse generator operation to a fixed duty cycle operation whereupon the meter will be held to a full scale deflection. When the triggering inputs decrease below the preselected frequency, the pulse generator will be returned to a triggering output mode.