Radio Control
Wireless radio remote control is used mostly in garage door openers, alarm systems, and remote control vehicles. In garage door openers and alarms, a simple tuned transmitter is used which sends a signal to a receiver via radio that is of a certain frequency usually around 400 MHz for garage door openers and alarms and about 75 MHz for radio control models, but they can vary depending on the manufacturer. The radio signals are differentiated using a special digital coding system. For example, inside of a garage door opener, there will most likely be a series of switches that are used to set the code for the opener. The code is in binary and this allows the openers to tell the difference between different openers. It is possible for one garage door opener to open the garage door at someone else's house as long as the two openers are set to the same frequency.
For the controller to work, the transmitter creates a serial pattern of ones and zeros using a digital circuit. This code is then sent to the receiver where the pattern is recovered and sent to the decoder circuit. When the circuit that was sent is sent using the same code (the one that was set on the inside of the transmitter), the action that you would like to carry out is carried out.
In remote control models, like boats, airplanes, and cars, the code that is sent out is sent in pulses that have to indicate position, like how far you turn the wheel on the joystick or how far you push the control lever. The code can be changed by simply changing the timing of the pulses or as complicated as sending the actual value of the angle of the control lever using binary numbers. All the information is incorporated into one continuous stream of data and is sent to the receiver.
The receiver then picks up the signal and feeds it into the decoding circuitry that separates the various channels and positions all the information. The information is analyzed and then tells the motors that do the controlling what to do.
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