69

There are two main reasons for the rise of serial 1) It's possible. Low cost transistors have been able to manage GHz switching for a decade now, long enough for the capability to be used and become standard. 2) It's necessary. If you want to shift very high speed data more than a few inches. This distance starts to rule out mobo to PCI card links, and ...


60

Parity. The word is Parity. Hopefully it was just misheard.


48

You would do a BERT (bit error rate test) on the cable. Better yet, look at the eye diagram at the far end of the cable. HDMI is a digital format, which means that there's a threshold effect — cable quality does not affect the picture quality at all until it gets so bad that it actually causes bit errors. "Premium" cable is (supposedly) built to ...


44

Mercury delay line memory used sound pulses in mercury to transfer bits. The advantage of this (compared to electrical signals) is the relatively slow propagation speed of 1 450 m/s while electrical signals travel at speeds above 100 000 000 m/s. This slow speed was taken advantage of to create memory. An emitter and receiver were connected using a column ...


36

It's used in oil drilling operations. Telemetry data from the drill head is transmitted as sound waves that propagate through the coolant. Data rates are abysmal (~10 bits per second) because a lot of frequency spreading is needed to get a signal that can be separated from the noise of the actual drilling. It is part of Measurement While Drilling (MWD) ...


33

I'm not an electronics engineer, but I would go for using the TX operation as a software UART. For an RX operation, buffering is needed, and interrupts are needed not to miss information. This is typically handled by a hardware UART. For a TX operation, you only need to send information, which is happening when you want it (for receiving you don't know ...


31

RF comms do not transmit one bit of information per cycle of the carrier wave - that would be digital baseband communications and it requires incredible amounts of bandwidth. Incidentally, you can buy FPGAs with built-in 28 Gbps serdes hard blocks. These can serialize and deserialize data for 100G ethernet (4x25G + coding overhead). I suppose the '...


30

Why there are no widespread system communication protocols that heavily employ some advanced modulation methods for a better symbol rate? If the basic copper connection between two points supports a digital bit rate that is in excess of the data rate needed to be transmitted by the "application", then why bother with anything else other than standard ...


29

16-QAM transmits 4 bits simultaneously by modulating both the phase angle and the carrier amplitude: - At the receiving end, the noise added during transmission propagation may make the bits look like this: - But, providing there is still a gap between data received and the halfway point between symbols you can detect it. So, if you understand the noise ...


27

brhans is correct - Legacy. In the 1980s, Hayes began making the "Smartmodem 1200". It was obsolete almost immediately and Hayes rushed out the Smartmodem 2400. In that rush, there was no time for design alterations between the modem designs. As a result, Hayes were the first to make two different speed modems that accepted the same programming commands! ...


27

HDMI cables are tested at an Authorized Testing Center (ATC) and given a certification based on how much bandwidth they can handle (which is to say, how high of a frequency signal they can transmit without the signal degrading beyond some parameters specified in the standard). Signals in a cable degrade. The signal that is input to the cable is not ...


24

If you want an example of something that is widely used, but different, look at 1000BASE-T gigabit Ethernet. That uses parallel cables and non-trivial signal encoding. Mostly, people use serial buses because they are simple. Parallel buses use more cable, and suffer from signal skew at high data rates over long cables.


24

Read the Wikipedia entry on "Fluidics". You will find that a fluidic digital computer, named FLODAC, was built in 1964. You will also see descriptions of fluid versions of logic gates. These types of components were very useful in applications where electromagnetic interference and/or radiation levels were too high for electronics.


22

You can't send half a bit, but you can effectively pack two half bits in one bit before transmission or storage. You give an example yourself, so you effectively have answered your own question with a YES. A maybe somewhat easier way is to simple encode the value of two decimal digits in 7 bits. (Sort of binary coded dual-decimal).


21

Yes, it's "parity". The code adds a third bit to make the number of ones either even or odd: 00 -> 100 = 1 one = odd 01 -> 001 = 1 one = odd 10 -> 010 = 1 one = odd 11 -> 111 = 3 ones = odd 00 -> 000 = 0 ones = even 01 -> 101 = 2 ones = even 10 -> 110 = 2 ones = even 11 -> 011 = 2 ones = even


20

A recommended approach would be to use an optocoupler followed by a comparator (eg. LM339), or better, an integrated part such as the Fairchild Semi FODM8071 logic gate output optocoupler. The reason the optocoupler is recommended: There is likely to be a ground potential difference over a 50 meter cable, also the possibility of picking up EMI over the ...


20

You're talking only about the downsides of the command set. Consider the upsides: By using the AT command set, your communication device can immediately be put on any IP network via the OS's PPP implementation. The alternative is that in addition to designing a custom protocol interface, you have to write your own network device driver for every OS you want ...


19

You can use huffman coding so the numbers are with varying bit length. if you are aware of a digit that will occur more often than others it will help. example(with equal occurrence): 0 - 1111 1 - 1110 2 - 110 3 - 101 4 - 100 5 - 011 6 - 010 7 - 001 8 - 000 receiving-end example for getting the number 1: The first bit comes in and leaves only 0 ...


19

You could use a SIP switch instead of a DIP. The saving in board area would give you the space for your I2C interface (or a simpler interface like a shift register with input latch): The picture shows it horizontal but it actually mounts vertically.


18

UART timing for asynchronous data relies on knowledge of the data rate and having a clock that is typically 16 x faster. The top half of the picture shows how data is re-synchronised and the bottom half shows a badly synchronised system (13x clock rate) just as an example: - In the absense of any data edges, the correctly timed clock can sample the data ...


18

Sure. PSK and FSK (and other modulation methods, for that matter) can have more than two choices for the phase or frequency. If you have four choices, you can send two bits at once. Advanced telephone modems (before we all switched to broadband) could encode as many as 8 to 10 bits at a time, using 256 to 1024 different signalling states. QAM-256 diagram (...


15

Actually, the answer to your seemingly simple question is more complex than you'd readily believe! The short answer is that one signal at a time can be passed through a single signal wire, in one cycle. The amount of data that symbol represents depends on the protocol used. The long answer is that: 2-state protocols, like OOK (On-Off Keying), pass only one ...


15

Yes there are a few cases but I'm not sure you'd be happy with the answers. Before electronics was invented, large pipe organs used small lead tubes to carry the signal from the console to the relevant pipe. The system is called "Tubular pneumatic action" Each key on the manuals requires its own tube, and each "stop" required a tube as well. When the ...


15

It's far simpler to implement a UART transmission in software because you just bit-bang the output port until the bytes are sent. To implement a receiver, you have to do multiple checks on the bits as they arrive (such as waiting for the start bit) and parity checking and usually, you have to run at a much higher processing rate to ensure you can cope with ...


14

I'll expand on the other side of the question ... why not just add another signalling line to the interface? That can only be asked by someone who didn't live through all the permutations of signalling lines on a genuine 25-pin RS232 interface. In addition to TXD, RXD and Gnd, there were several other pairs of signals already, RTS/CTS (Ready to Send, Clear ...


14

I remember it as fluidic logic. Here's an old cover from Scientific American: Channels were formed in plastic and streams of air or fluid were used to "switch" the "circuits".


13

A Push-Pull output is your normal CMOS or TTL-like output. It's either HIGH (IO pin is connected to VCC through a MOSFET), or LOW (IO pin is connected to GND through a MOSFET). The basic circuit of the output stage is as simple as: simulate this circuit – Schematic created using CircuitLab It is the technical name for any "normal" digital output ...


12

Transmitting 10 Hz over 50 m is not a difficult problem, so you'll find there's numerous ways to do it. For a solution nearly as simple as the one you had before, I'd suggest a simple zener circuit. Like before, you'd simply supply your sensor with a voltage above 5 V. Say 6 - 12 V, and let this limiting circuit reduce the voltage to a level compatible with ...


12

Perhaps what you are looking for is Arithmetic Coding, which can efficiently encode a string of symbols, each of which in principle might require a fractional (non-integer) number of bits. (though the total message must be a whole number of bits) Quoting Wikipedia: Arithmetic coding differs from other forms of entropy encoding such as Huffman coding in ...


12

It's not (phase) (shift keying), for example. It's (phase shift) (keying). Another answer has explained why the word keying is used --- it dates to the days when modulation was controlled by a human operator using a telegraph key. The phase shift (or amplitude shift or whatever) is because something is changing (shifting) when keyed. If the system were ...


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