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1500 questions
24
votes
4 answers
Why do push button telephones use dual-tone for signalling?
Here is a related information from wikipedia:
For touchtone service, the signal is a dual-tone multi-frequency
signaling tone consisting of two simultaneous pure tone sinusoidal
frequencies.
Above shows that if one pushes number 1 he sends…
user16307
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24
votes
7 answers
How do I learn HDL
I have a course in Digital Design in this semester and just love it. Now I know that most of the work in embedded system and digital design is done on computer simulators first and then implemented using hardwares. So I was wondering how should I go…
Rick_2047
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24
votes
2 answers
How do I correct the offset voltage of op-amps which have no explicit offset-null pins?
Not all op-amps have explicit offset-null support, but all op-amps have an offset voltage.
This is exactly my practical circuit:
How do I correct the offset voltage of TL084 in this circuit?
(Datasheet: TL084)
hkBattousai
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24
votes
6 answers
How did old WW2-era radars accurately measure time delay and integrate this into an oscilloscope?
The speed of light is about 300,000 km per second. An error of just 1 ms would result in being off by about 300 km, which is far too much error for a radar. I would guess it needs accuracy on the order of 10 microseconds in order to get range…
DrZ214
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24
votes
1 answer
What is the purpose of the elements of this antenna?
I have a 5GHz 23dBi Wi-Fi panel antenna which has the geometry shown in the images below.
I have been quite curious as to the purpose of this bizarre antenna design. The elements have such unique shapes, and each is slightly different, though…
Sam Gallagher
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24
votes
5 answers
What set the speed in a cassette tape recorder?
I was wondering what set the rotational speed in a cassette recorder? I assume that the speed must be constant, but that means that the tape data would have different effective densities depending on where you were on the tape. Was it a stepper…
b degnan
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24
votes
8 answers
Advice on going from rat's nest to routed PCB
Can anyone offer any useful strategies on going from a rat's nest to a routed PCB?
(I'm using Eagle and aiming to make single/double sided PCBs at home)
Drawing the schematic is fine, but when it comes to routing the tracks, it feels like…
Toby Jaffey
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24
votes
8 answers
How do I build a computer with a Z80 microprocessor?
I've got the chip, so how would I add: a clock, RAM, hard drive (maybe EEPROM?), a screen (LCD graphical screen?), input method (keyboard, mouse) ?
user8210
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24
votes
3 answers
Why is the reflector on this millimeter-wave antenna spinning?
The WIRED YouTube video Inside Facebook's Quest to Beam the Internet Via Solar Drone and article Inside Facebook’s First Efforts to Rain Internet from the Sky show a dish antenna (starting after 02:00) with what looks like a Cassegrain secondary…
uhoh
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24
votes
9 answers
Measure voltage with no current
Suppose I have a capacitor and I want to observe its charge decay over time. How can I do that without affecting its discharge rate through measurement?
AFAIK a typical voltmeter runs current through a known resistance to determine voltage, but in…
feetwet
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24
votes
3 answers
How does a 40 Gbit/s Ethernet interface process packets in silicon?
A 40 Gbit/s Ethernet interface should have a 40 GHz signal on it. How does common silicon IC technology handle such an exotic beast?
My best guess is that internally various parallel busses are used, but I haven't found much on the internals of…
Watson Ladd
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24
votes
5 answers
When/why would you use a Zener diode as a flywheel diode (on the coil of a relay)?
I have just been cogitating on the tutorial at http://www.electronics-tutorials.ws/io/io_5.html, and in the discussion of flywheel diodes it includes this sentence without further elaboration:
As well as using flywheel Diodes for protection of…
Kaelin Colclasure
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24
votes
5 answers
Effect of bootstrapping in amplifier circuit
I am trying to understand this "bootstrap bias" amplifier circuit. The picture below is adapted from the book "Transistor Techniques" by G. J. Ritchie:
This circuit is a variation of the "voltage divider bias", with the addition of the…
favq
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24
votes
4 answers
Why are there no BGA chips with triangular tessellation of circular pads (a "hexagonal grid")?
Ball grid arrays are advantageous integrated circuit packages when a high interconnect density and/or low parasitic inductance is paramount. However, they all use a rectangular grid.
A triangular tiling would allow π⁄√12 or 90.69% of the footprint…
jms
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24
votes
7 answers
Why do brushless motors have a kv rating?
I am wondering why brushless motors, such as ones used for quadrotors, have a kv rating, which supposedly means RPM per voltage across the motor. So a 2300 kv motor spins at 2300 rpm if "1 volt is applied" to it.
The part in parenthesis does not…
Thomas Kirven
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