Frequency is not unlimited. For example the devices responding to the remote (photo-diodes) are relatively slow when they have a low amount of light, so this limits the upper frequency if a reasonable range and battery life is expected. Ditto the lower limit is "still fast enough to carry a sufficiently large code in a sufficiently short time". In similar ways all devices have limited frequency ranges. Carrier frequencies of remotes are shared, the codes are unique, so the button pressed is identified in the coding as for "Sony model xyz TV volume up" etc.
Tesla's tele-automaton was one of the very first applications of radio ever, as opposed to demonstrations of radio things that many others were involved in around 1898. He used a simple stepping code in a sequence. The transmitter just sent a "blip" when required. He recognized that the frequency of the radio wave could be used to address a particular unit (boat). It was a code with two transmitters and their receivers of different frequencies that had to coordinated for a code to be recognized. This could have allowed a few of his boats to operate independently at the same time. The receiver operated a relay mechanism each time a "blip" was received. There was a motor driven mechanical rotary switch in the receiver that stepped for each recognized blip, so something like: first blip rudder left, second blip rudder right, third blip rudder center, fourth blip forward, fifth blip stop and so on back to the first blip. I am fairly sure the second radio channel was used to enable the selected control.
The fact that most remotes operate on IR bulbs helps. Very rarely will you get an actual RF remote with your equipment. The IR bulb flashes a signal to the IR receiver on the piece of equipment. The flashing codes are no industry secret, so when you "program" your universal remote, you are just telling it to flash in a sequence that the manufacturer has intended for that equipment. A universal RF remote would need to have both an adjustable clock function to make the carrier frequency of the unit in question and be able to heterodyne the command functions into that carrier, almost the same way that you get FM radio.
Infrared remotes are pre-programmed with digital 'words' that are unique for the brand of device(s) you are trying to program. The codes that you enter from the maker of the programmable remote sets up the actual IR frequencies to match the brand(s) of your device. The programmable remote then sends a 'digital word' when you press the buttons on the programmable remote that match the standard codes the manufacturer of the device(s) have codes their devices with. ANSWER #2. there are 'Learning Remotes' on the market. You hold a working remote up to it and press the corresponding buttons and it 'learns' or stores the actual code emitted by the original remote. Here is a neat trick. The camera on your cell phone can 'see' infrared. Turn on your camera on your phone and point the remote directly at the lens and push a button on the remote. You will see the IR LED flash the digital code.
It is one frequency, one LED, common to all devices. Each controller sends out a pattern of "blinks", a digital sentence, much like an ethernet data packet, that is keyed to a specific device.
A universal remote will choose the "sentence" to send for each key press, based on what brand of TV you tell it you want to talk to.
Iniversal remote controllers work on IR not frequency.
If remote controllers are all tuned to different frequencies, how does a universal remote work on any television? I am just reading about Nikola Tesla right now, and have become aware of his teleautomaton invention, and I became intrigued.
Thank you.
