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Evolution of Mobile Networks: The First Generation (1G): ·          In the United States, and analog cellular mobile communication service called advanced mobile phone service (AMPS) was started in October, 1983. ·          In Europe, several cellular mobile communication services were started. In Norway, Nordic Mobile Telephones (NMT) succeeded in the development of an analog cellular mobile communication system: NMT - 450 [7]. ·          In the United Kingdom, Motorola developed an analog cellular mobile communication system called the total access communication system (TACS) based on AMPS in the 1984-1985 periods. In 1983; NMT started a modified NMT - 450 called, NMT - 900 Moreover C-450, RTMS and Radio com - 2000 were respectively introduced in Germany, Italy, and France. ·          Meanwhile, in Japan Nippon Tel...

stepper motor

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Stepper motor drivers often have different modes of operation. These different modes determine in what sequence the coils are energized to make the motor shaft move appropriately. There are four types of these stepping modes. However, only three of the excitation modes are common in most stepper drivers. Step Modes Wave Drive This method of stepping the motor energizes one phase at a time. This method is rarely used and most likely will not be on modern drivers. This method is very inefficient and produces less torque than other methods. Full Step This method of stepping the motor energizes both phases constantly to achieve full rated torque at all positions of the motor. If a stepper motor has 200 steps, one pulse equals one step. So, 200 pulses from the NC computer results in 360 degrees of motor shaft rotation. A uni-polar stepper motor driver operating in full step mode energizes a single phase. A bipolar stepper motor driver energizes both...