A rheostat is an electrical component that has an adjustable resistance. It is a type of potentiometer that has two terminals instead of three. The two main types of rheostat are the rotary and slider. The symbol for a rheostat is a resistor symbol with an arrow diagonally across it. Rheostats are used in many …
A thermoelectric generator is a solid-state device that works similar to solar panels but converts heat, rather than sunlight, directly into electricity. A thermoelectric generator is usually made of bismuth telluride semiconductor junctions that are only several millimeters thick. This differs drastically from the bimetallic junctions that were previously used, which were much thicker. Thermoelectric …
A retrograde orbit is an orbit where the satellite travels in an East to West direction instead of the common West to East orbit. The normal West to East orbits are known as prograde orbits. Retrograde orbits are uncommon due to the much higher velocities necessary for successful launch and the associated higher costs. During …
Variac is the trademark name of a variable autotransformer. A variable autotransformer is a single-coil transformer in which two portions of the same coil are used as the primary and the secondary. Variable autotransformers are used for the same purposes as regular transformers, but handle lower voltages. They also differ from regular autotransformers in that …
A battery isolator is used to prevent primary battery systems from being drained and are mostly used in car stereo systems. These devices cause a secondary/auxiliary battery to be drained instead of the vehicle’s primary battery. This is so whether the stereo is used when the engine is turned off or if an after-market stereo …
Satellite images are taken by reconnaissance satellites that orbit the Earth at a relatively low altitude, between 300 to 600 miles (or 480 to 970 km). As the majority of today's satellites are custom made in order to accommodate particular needs of the designer, there is no standard on which photo imagery is based on …
In order to deter theft, the majority of major automobile manufacturers implement a car radio security code. When the car stereo is removed from a vehicle, the device will not be usable until the unlock or security code is entered by the car owner or authorized repair facility. Unfortunately, some models of cars and trucks …
dBm is the standard unit of measure for levels of power based on a one milliwatt (mW) reference signal. The dBm measurement is very similar to dB (decibel); however, dB is a relative measure of the power of an input signal while dBm is always an absolute value based on a single milliwatt. If there …
A heterodyne is a circuit that transfers a signal from one carrier wave to another with a different frequency. It mixes the input signal with a wave generated by an oscillator to create two new signals, called beats. While heterodyning is a simple process governed by the laws of trigonometry, most heterodynes are complex devices …
A multivibrator is an electronic circuit that rapidly switches because of positive feedback between multiple states. The switch’s output is harmonic. Three types of multivibrator circuits are used in industry today: astable, monostable, and bistaple. Types of Multivibrators The three multivibrator types are: Astable Multivibrator – The circuit is not considered stable in either of …