Abstract: A parking lamp operating system reduces the electrical load on the battery of a vehicle, such as a truck, during periods when the vehicle engine is off but the parking lamps of the vehicle remain on wherein a switched signal input from the battery is modulated to provide a pulse-width-modulated output to the gate of a power transistor having a power input from the battery and an output to the parking lamps. The pulsed signal causes the transistor to intermittently switch the power to the lamps thereby reducing the effective voltage thereto while providing sufficient light output to be observed. The modulator may be bypassed by a second signal line connected to the vehicle alternator to provide a continuous signal to the transistor gate, thereby providing full power to the lamps when the engine is running.

Abstract: A device for sensing the speed of a rotating element in a vehicle replaces the practice of using magnetic wire coil pickup devices placed in close proximity to a rotating element, such as a gear. The main speed sensing component is a conventional three lead Hall effect device which produces a voltage each time it is exposed to the presence of a magnetic force which exceeds a predetermined value. The adoption of a device which produces the Hall effect introduces the complication of harmonizing the connection of the three leads of the standard Hall effect device with the connections conventionally found in existing installation of only two leads between the sensing unit and the controlled element. Transistor diode and resistive components mounted in the same housing as the Hall effect device provide a configuration entirely compatible with existing two lead systems.

Abstract: A trailer stability monitor for tractor-trailer vehicles including a motion sensor and signal responsive r.f. transmitter responsive thereto mounted on the trailer and a r.f. signal receiver coupled to alarm means and mounted on the tractor, preferably in the cab thereof, for receiving the signal from said transmitter and causing an alarm to warn the operator of the tractor-trailer of conditions conducive to rollover to permit remedial measures to be undertaken to avoid such incident. The motion sensor includes a pair of angular mounted normally open mercury switches arranged to detect lateral forces to the right or left to a degree conducive to rollover. A vertically oriented normally closed mercury inertia switch is connected in series with the pair of angular mounted parallel connected switches to momentarily disable the circuit to prevent spurious signals from bumps. The switch array is connected in series with a battery and a lower power r.f.