Abstract: An improved vehicle compass calibration obtains magnetic field data measurements from magnetic field sensors mounted in a vehicle. The magnetic field data measurements are stored in memory and, when a sufficient set of data measurements is stored, a calibration calculation attempt is carried out. When a predetermined vehicle accessory that produces a magnetic disturbance is activated, the storage of magnetic field data in memory is interrupted to disable the ongoing collection of data for use in a subsequent calibration calculation while the accessory remains activated.

Abstract: A variable inductance device for indicating the position of one body relative to another includes primary and secondary windings which are mounted such that one is slidable over the other. The primary winding is wound on a body including annular channels for retaining the winding turns in an arbitrarily selectable turns distribution. The secondary is a shorted winding. A signal producing circuits electrically connected to the primary winding for producing a signal which varies with the device inductance. By selecting the turns distribution such that the device's inductance variation with position and the signal producing circuit's output variation with inductance complement each other, the output signal is made to vary as an arbitrarily selectable function of the position.

Abstract: A predetermined frequency alignment signal and a white noise source signal are alternately switched through the intermediate frequency amplifier stage (IF) of the receiver being aligned. A series connected integrating capacitor and tuning meter couple between the receiver's detector output and ground potential.In operation, during the interval of white noise being applied to the IF the tuning meter is shorted and the capacitor is charged to a net voltage V.sub.n which is representative of the center frequency of the IF. When the alignment signal is applied to the IF, the tuning meter short is removed and a signal V.sub.s appears across the capacitor-meter circuit, whereby the meter reading is indicative of V.sub.s -V.sub.n which represents relative receiver alignment.