Abstract: An apparatus for checking a trouble in a communication circuit connected between engine and transmission control units. A check signal is produced at uniform intervals of time. The check signal is converted into a predetermined code. The converted code is transmitted through the communication circuit from one of the engine and transmission control units to the other control unit. The code transmitted to the other control unit is monitored to produce a failure signal to indicate that a trouble occurs in the communication circuit when the monitored code is not identical with the predetermined code.

Abstract: By using subassemblies that can be mounted on the floor of the vehicle or on the brake lever and the accelerator lever a continuously active and quick acting alerting system is developed in which an operator sets a time which is needed to switch over the foot between the accelerator and brake pedals and when operator does not accelerates or apply brakes uses an auxiliary device which can be operated by the same foot to indicate alertness and failure to do so within the set time results in actuating alarming devices. Whenever the accelerator or the brake pedal or the auxiliary device is actuated the timer resets itself. The time set is usually within five seconds.