So, couldn't the sofware that feeds the gear that generates the FSK info tell it about the ANI data that it would send to a PRI rather than whatever the originator sent?
I suppose there's no technical reason why not, but as mentioned elsewhere in this thread:
You can't send both via the CallerID protocol. CallerID only supports ten digits.
Telcos have allowed PBX's to set CallerID on outgoing calls so that they can set it to the caller's DID (direct-inward-dial) number so the receiver of the call gets the caller's number (f.e. 555-2391) instead of the business's main number (f.e. 555-2000) on the Caller ID display. The ANI information must remain the main trunk number as that's what is used for telco billing, 911, etc.
Telcos should have filtered outgoing CallerID based on the DID blocks that the customer actually owns (f.e. 555-2XXX) but most haven't been doing that.
So basically, there is a need to maintain two separate numbers for the originator of the call, CallerID can only show one of them, and you can't trust the one your telco has chosen to show you because telcos as an industry have been careless about it.
So I want the ANI info in my CallerID line. Why is this hard, or why are the Baby Bells unwilling to do it?
Because they didn't create a way to do it that was backwards-compatible.
CallerID is sent as 1200baud FSK between the first and second rings. ANI is, for E&M trunk lines, sent as DTMF codes by the phone switch, or for BRI/PRI trunks, sent digitally with the other call connection information. DTMF incurs a significant connection delay - sending ANI plus DNIS (dialed number identification service, basically telling you which number the call was placed to) means sending 17 or more DTMF tones - so PRI is the preferred method.
So ANI in its current form really only works with trunk lines. In some areas with some ILECs trunks can be analog (leaving you stuck with E&M DTMF) but otherwise you're looking at the expense of ISDN or a T1.
The current CallerID protocol is flawed in that if you answer the call before the second ring, you don't get the CallerID information. I don't know why the telcos released such a flawed protocol or why they aren't interested in fixing it today. Maybe they figured that ISDN would replace POTS by now. Instead, as you mentioned, probably VoIP will instead.
I'm curious. Where? Froogle has listings for the GPS 18 starting at $78 and for the GPS 35 starting at more like $169. It looks like you can get the mount for under the $25 mentioned by the grandparent post, but that's about it.
Assuming those exist, I wonder if once you wired them all in series (2.5V isn't exactly practical:) what the internal resistance would be.
I've got a 4.7F 2.5V supercap sitting on the workbench. It is 34mm long and 12mm in diameter, or 3.8 cm^3. Assuming a supercap could scale linearly with size, a 2000F supercap made the same way would be about 1600 cm^3, and 30 of them would be about 48 000 cm^3, or about the same size as one of my filing cabinet drawers.
Couldn't you push the regenerative braking power into a supercap, and then push the supercap's power into the lead acid battery?
A 1200kg car with traditional brakes traveling 26.8 m/s (60mph) converts 431 kilojoules to heat as it stops. A motor could convert perhaps 90% of that to electrical energy instead.
For a capacitor system that might top out at 200V after such a charge (to charge, say, a 144V battery system), you'd need about 20 farads of capacity. (E=C*V*V/2)
Keep in mind that cars may be heavier than 1200kg (2500 pounds) and may go much faster than 26.8 m/s.
It pretty much only works with gas. Say your shower is 2.5 gallons per minute, or approximately 10 liters per minute. Say you need the water to be 110F (43C) (in the pipe) to feel hot by the time it hits your face. Say incoming water is 55F (13C). You need to raise the temperature of 10 kilograms of water 30C every minute, or 1 kilogram by 5C per second. That's 5 kilocalories per second, or 21 kilowatts. For a 240V heating system, that would require 87 amps, which is a significant (some would say scary) fraction of the average home's electrical service.
For reference, the natural gas furnace in my home is capable of 55000 BTUs per hour, or 16 kilowatts. A load 31% larger is certainly within the realm of practicality.
My next gun will be compressed air, and once I figure it out with PVC, I'm moving on to stainless steel to hopefully get a supersonic potato (or other projectile) gun:-)
I've been idly investigating this myself. It looks like there are high-pressure solenoid valves available that are commonly used in hydraulic systems and Nitrous Oxide applications. They have ratings as high as 4500 PSI. The larger ones can be very expensive, but for a reasonable application such as this one, one might be able to keep the valve's cost around $100ish.
It would take a fairly expensive compressor to get the air to that pressure, though.
And no, I haven't done the calculations on the pressure and barrel lengths required to get a potato supersonic yet.:)
I'm looking forward to UWB, as it is a (from what I understand) a low/no intereference solution
There is no such thing as a free lunch.
Currently, you get a chunk of spectrum and you do whatever with it. If someone interferes, you track that one person down and get them to stop. The size of your spectrum effectively limits the bitrate you can throw across it, assuming consistent power/noise ratios, because after all, if no one is interfering, noise stays consistent.
A UWB transmitter raises the noise floor across all bands ever so slightly, basically proportionately to the bitrate and range the transmitter seeks. Not really a problem for a few transmitters. Also, since people transmit so infrequently, lumping everything together means you're less likely to be affected by the interference.
But if UWB becomes commonplace, and people become greedy for higher bitrates, then keeping the noise floor low for the people still using fixed spectrum allocations will become a forgotten priority. And even if UWB becomes truly universal, if the noise floor gets too high, where do you start to fix it? How do you decide which UWB transmitters are talking too loudly and for too long? If you start to license how much power and time they can use, how do you determine that a given licensee (or an anonymous unlicensed user) is the problem?
Some analogies:
If allocated spectrum is like having slow individual PC's, UWB is like being on a fast mainframe while the admin is on vacation.
If allocated spectrum is like a stain on a shirt, UWB is what the stain looks like after it bleeds to all the other clothes you washed with it.
If allocated spectrum is like a monthly marital spat, UWB is like the loud party the neighbors are always having.
What prevents a competor with a wireless broadcast anteanna from parking in range of your factory, and sending false signals telling your machines to idle?
BTW, I'm pretty sure that the article had a typo - they probably meant IEEE 802.15.4 (aka Zigbee), not 802.16.4. The Zigbee FAQ has a lot of valuable information about it.
I call BS. Extraordinary claims require exactly the same solid, persuasive evidence as all other claims.
Solid and persuasive evidence is, it seems, quite rare and extraordinary. For example in this case we have a breadth of anecdotal evidence but no quantifications - no statistics.
The phrase was popularized by Carl Sagan. Read a paper on it.
Risk = probability * loss. Since loss is obvious and fairly constant (a flaky or inoperative computer), if you want to hype this risk, besides just showing clear evidence that zinc whiskers are increasing the probability that a computer will die, you have to show to what degree that probability is increased - that is, that it merits more concern than other obscure things that can cause a computer to die.
Remember, the only reason the public Internet exists is because the FCC, over the *strenuous* objections of the Bell System, overrode restrictions on "sharing" of leased lines.
Recently it seems the FTC is taking more of these kinds of actions than the FCC. The FTC seems just as well-equipped to regulate natural monopolies like ILECs as the FCC.
Yes, it will pump maybe a tenth of its power (perhaps 100mW, tops, so 10mW) into you, which will be converted to heat, cooking you.
Some other things that you should avoid would be flashlights, which can pump upwards of a watt of very concentrated RF into you, or even worse, the sun, which is capable of directing over 500 watts your way, burning you and contributing to your cancer risk!
To prevent this, you should stay away from all electronic devices, especially communication devices, as even an LED or computer monitor may exceed 10mW of radiated power. After all, we want you to live as long as possible. Without hearing from you ever again.
See, I'm trying to get a wireless connection to my friends network about three miles away, directly. We can't erect 100' towers so we're trying to figure out our options. We can mount the things on our roofs but we won't have direct line of sight (some trees, the curve of the earth, etc..)
You won't be able to make this work at microwave frequencies. Directional antennas and amps simply won't help. UHF or VHF frequencies might work, however the lower the frequency you use, the more precious (and scarce) the bandwidth becomes.
Once the FCC's new vision for reusing TV channel bandwidth for wireless networking becomes reality, you'll be able to buy equipment that will probably do 3 miles via ground wave propagation just fine.
In the meantime, your options are very limited. You could buy two old Metricom Ricochet modems and run PPP between them (slow!). Since you said you don't care about the FCC, you could build your own equipment, but if you knew how to do that you probably wouldn't have asked us. If the two buildings can see a common point, perhaps you could place a solar/battery-powered wireless repeater there.
Or, do what everyone else does and set up an IPSec tunnel over the Internet.
One billion bits per second can not be shoved onto four hundred million cycles per second.
Sure it can. Modems, for example, have done multiple bits per baud since they passed 2400bps. The only limit to how far you can go with this is signal to noise ratio.
the highest-bandwidth signal that can theoretically be put on a given carrier frequency is equal to half of that frequency.
No, the highest frequency that you can sample is equal to half of the sampling rate.
You are confusing Shannon with Nyquist. Read up on both. Also read up on the term 'baseband'.
The frequency of radio waves has absolutely nothing to do with data transmission speed. Nothing.
That's absolutely incorrect.
No, it's correct. Transmission speed is a function of bandwidth and signal to noise ratio (see Shannon's Law).
For example, you can broadcast at the same rate with the same received signal to noise ratio on channel 4 (66-72mhz) as you can on channel 22 (518-524mhz) because both channels are 6mhz wide.
Granted, there is more room for more bandwidth at higher frequencies...
"kilo", "mega", "giga", etc., in the context of communication links has always meant 10^3, 10^6, and 10^9, never 2^10, 2^20, and 2^30 or any weird combination thereof.
For confirmation of this, just run snmpwalk on your router and look at interfaces.ifTable.ifEntry.ifSpeed.
Their reporting of the dataset size reflects this culture.
I'm glad you think it's easy. Bugatti who knows a little about such matters [...] seem to think it a great challenge.
The people who know how easy it is to create 400kg of lift at those speeds aren't exactly Bugatti's target sales demographic.
400lbs downforce at 340 f/s at sea level with 5 sq. ft. of wing (guessing here) is only a lift coefficient of 0.6.
I'd be willing to bet you could get that with a 5 foot long 2x12 board.
Re:Small engine, fast cars but what about airplane
on
The Bugatti Veyron
·
· Score: 5, Interesting
60 years ago when internal combustion propellor planes were the standard, I'm guessing that the prop plane defined the hi-tech, high powered, low weight internal combustion engine. Anyone know if that's still true?
If you're referring to General Aviation propellor aircraft, the answer is definately no.
Chances are that the Lycoming or Continental engine in your average Cessna has changed very very little over the past 50 years. Even though intercooling and turbocharging are more common options today, they are still air-cooled, still cruise at 2500-3000rpm, and still magneto-fired. If you took a time machine, kidnapped an A&P from 1950 and put him here, he would probably die from the shock of everything being exactly the same. If not, he would begin a spree to kill all of the lawyers responsible.
By comparison, your car's engine is about 25% more fuel-efficient, can produce 50-100% more power per unit of displacement thanks to its higher speed, is liquid-cooled, is often variably-timed, will run on unleaded low-octane fuel, and is probably much quieter than an aircraft engine.
Many automotive engines, from Honda Goldwing engines to Chevy 350 cu. in. V8's and on up, are converted to air use in Experimental Aviation. They usually must be geared down to swing a decent-sized prop at a reasonable mach number (supersonic prop tips are bad). Some pilots do this because of the costs of a certified engine ($20k+, plus regular maintenance by an A&P), some do it because 100LL avgas is so expensive, some do it because they believe the end result will be more trustworthy.
As for rotaries, yes, they'll save you a bunch on weight (and size, if needed), and some people put them in experimental aircraft. They have very few moving parts which increases reliability. Unfortunately the combustion chamber in a rotary has so much more surface area (per unit of displacement) than the equivalent reciprocal engine that rotaries will probably continue to lag 15-20% behind reciprocal engines on fuel efficiency.
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I suppose there's no technical reason why not, but as mentioned elsewhere in this thread:
So basically, there is a need to maintain two separate numbers for the originator of the call, CallerID can only show one of them, and you can't trust the one your telco has chosen to show you because telcos as an industry have been careless about it.
Because they didn't create a way to do it that was backwards-compatible.
CallerID is sent as 1200baud FSK between the first and second rings. ANI is, for E&M trunk lines, sent as DTMF codes by the phone switch, or for BRI/PRI trunks, sent digitally with the other call connection information. DTMF incurs a significant connection delay - sending ANI plus DNIS (dialed number identification service, basically telling you which number the call was placed to) means sending 17 or more DTMF tones - so PRI is the preferred method.
So ANI in its current form really only works with trunk lines. In some areas with some ILECs trunks can be analog (leaving you stuck with E&M DTMF) but otherwise you're looking at the expense of ISDN or a T1.
The current CallerID protocol is flawed in that if you answer the call before the second ring, you don't get the CallerID information. I don't know why the telcos released such a flawed protocol or why they aren't interested in fixing it today. Maybe they figured that ISDN would replace POTS by now. Instead, as you mentioned, probably VoIP will instead.
I'm curious. Where? Froogle has listings for the GPS 18 starting at $78 and for the GPS 35 starting at more like $169. It looks like you can get the mount for under the $25 mentioned by the grandparent post, but that's about it.
I've got a 4.7F 2.5V supercap sitting on the workbench. It is 34mm long and 12mm in diameter, or 3.8 cm^3. Assuming a supercap could scale linearly with size, a 2000F supercap made the same way would be about 1600 cm^3, and 30 of them would be about 48 000 cm^3, or about the same size as one of my filing cabinet drawers.
A 1200kg car with traditional brakes traveling 26.8 m/s (60mph) converts 431 kilojoules to heat as it stops. A motor could convert perhaps 90% of that to electrical energy instead.
For a capacitor system that might top out at 200V after such a charge (to charge, say, a 144V battery system), you'd need about 20 farads of capacity. (E=C*V*V/2)
Keep in mind that cars may be heavier than 1200kg (2500 pounds) and may go much faster than 26.8 m/s.
Good luck spec'ing out that supercapacitor.
It pretty much only works with gas. Say your shower is 2.5 gallons per minute, or approximately 10 liters per minute. Say you need the water to be 110F (43C) (in the pipe) to feel hot by the time it hits your face. Say incoming water is 55F (13C). You need to raise the temperature of 10 kilograms of water 30C every minute, or 1 kilogram by 5C per second. That's 5 kilocalories per second, or 21 kilowatts. For a 240V heating system, that would require 87 amps, which is a significant (some would say scary) fraction of the average home's electrical service.
For reference, the natural gas furnace in my home is capable of 55000 BTUs per hour, or 16 kilowatts. A load 31% larger is certainly within the realm of practicality.
I've been idly investigating this myself. It looks like there are high-pressure solenoid valves available that are commonly used in hydraulic systems and Nitrous Oxide applications. They have ratings as high as 4500 PSI. The larger ones can be very expensive, but for a reasonable application such as this one, one might be able to keep the valve's cost around $100ish.
It would take a fairly expensive compressor to get the air to that pressure, though.
And no, I haven't done the calculations on the pressure and barrel lengths required to get a potato supersonic yet. :)
You say "your project is doomed" to anyone with a project? :)
There is no such thing as a free lunch.
Currently, you get a chunk of spectrum and you do whatever with it. If someone interferes, you track that one person down and get them to stop. The size of your spectrum effectively limits the bitrate you can throw across it, assuming consistent power/noise ratios, because after all, if no one is interfering, noise stays consistent.
A UWB transmitter raises the noise floor across all bands ever so slightly, basically proportionately to the bitrate and range the transmitter seeks. Not really a problem for a few transmitters. Also, since people transmit so infrequently, lumping everything together means you're less likely to be affected by the interference.
But if UWB becomes commonplace, and people become greedy for higher bitrates, then keeping the noise floor low for the people still using fixed spectrum allocations will become a forgotten priority. And even if UWB becomes truly universal, if the noise floor gets too high, where do you start to fix it? How do you decide which UWB transmitters are talking too loudly and for too long? If you start to license how much power and time they can use, how do you determine that a given licensee (or an anonymous unlicensed user) is the problem?
Some analogies:
If allocated spectrum is like having slow individual PC's, UWB is like being on a fast mainframe while the admin is on vacation.
If allocated spectrum is like a stain on a shirt, UWB is what the stain looks like after it bleeds to all the other clothes you washed with it.
If allocated spectrum is like a monthly marital spat, UWB is like the loud party the neighbors are always having.
Standardized AES encryption.
BTW, I'm pretty sure that the article had a typo - they probably meant IEEE 802.15.4 (aka Zigbee), not 802.16.4. The Zigbee FAQ has a lot of valuable information about it.
Wow. How did you increase the local atmospheric pressure to 400 bars to allow for the higher SPL?
Solid and persuasive evidence is, it seems, quite rare and extraordinary. For example in this case we have a breadth of anecdotal evidence but no quantifications - no statistics.
The phrase was popularized by Carl Sagan. Read a paper on it.
Extraordinary claims require extraordinary evidence.
Risk = probability * loss. Since loss is obvious and fairly constant (a flaky or inoperative computer), if you want to hype this risk, besides just showing clear evidence that zinc whiskers are increasing the probability that a computer will die, you have to show to what degree that probability is increased - that is, that it merits more concern than other obscure things that can cause a computer to die.
Recently it seems the FTC is taking more of these kinds of actions than the FCC. The FTC seems just as well-equipped to regulate natural monopolies like ILECs as the FCC.
Yes, it will pump maybe a tenth of its power (perhaps 100mW, tops, so 10mW) into you, which will be converted to heat, cooking you.
Some other things that you should avoid would be flashlights, which can pump upwards of a watt of very concentrated RF into you, or even worse, the sun, which is capable of directing over 500 watts your way, burning you and contributing to your cancer risk!
To prevent this, you should stay away from all electronic devices, especially communication devices, as even an LED or computer monitor may exceed 10mW of radiated power. After all, we want you to live as long as possible. Without hearing from you ever again.
You won't be able to make this work at microwave frequencies. Directional antennas and amps simply won't help. UHF or VHF frequencies might work, however the lower the frequency you use, the more precious (and scarce) the bandwidth becomes.
Once the FCC's new vision for reusing TV channel bandwidth for wireless networking becomes reality, you'll be able to buy equipment that will probably do 3 miles via ground wave propagation just fine.
In the meantime, your options are very limited. You could buy two old Metricom Ricochet modems and run PPP between them (slow!). Since you said you don't care about the FCC, you could build your own equipment, but if you knew how to do that you probably wouldn't have asked us. If the two buildings can see a common point, perhaps you could place a solar/battery-powered wireless repeater there.
Or, do what everyone else does and set up an IPSec tunnel over the Internet.
Sure it can. Modems, for example, have done multiple bits per baud since they passed 2400bps. The only limit to how far you can go with this is signal to noise ratio.
the highest-bandwidth signal that can theoretically be put on a given carrier frequency is equal to half of that frequency.
No, the highest frequency that you can sample is equal to half of the sampling rate.
You are confusing Shannon with Nyquist. Read up on both. Also read up on the term 'baseband'.
That's absolutely incorrect.
No, it's correct. Transmission speed is a function of bandwidth and signal to noise ratio (see Shannon's Law).
For example, you can broadcast at the same rate with the same received signal to noise ratio on channel 4 (66-72mhz) as you can on channel 22 (518-524mhz) because both channels are 6mhz wide.
Granted, there is more room for more bandwidth at higher frequencies...
s/several/all/
Picture a lightning bolt. It's white, right? White is the sum of all colors. White (RF) noise is the sum of all frequencies.
1100 watts/m^2 * .23m * .3m = 76 watts
76 watts of solar power * .5 (50% efficiency the article mentions) = 38 watts of electrical power.
And that's if this research pans out and if the price becomes practical and if you aim it directly at the sun on a perfectly sunny day.
For confirmation of this, just run snmpwalk on your router and look at interfaces.ifTable.ifEntry.ifSpeed.
Their reporting of the dataset size reflects this culture.
The people who know how easy it is to create 400kg of lift at those speeds aren't exactly Bugatti's target sales demographic.
400lbs downforce at 340 f/s at sea level with 5 sq. ft. of wing (guessing here) is only a lift coefficient of 0.6.
I'd be willing to bet you could get that with a 5 foot long 2x12 board.
If you're referring to General Aviation propellor aircraft, the answer is definately no.
Chances are that the Lycoming or Continental engine in your average Cessna has changed very very little over the past 50 years. Even though intercooling and turbocharging are more common options today, they are still air-cooled, still cruise at 2500-3000rpm, and still magneto-fired. If you took a time machine, kidnapped an A&P from 1950 and put him here, he would probably die from the shock of everything being exactly the same. If not, he would begin a spree to kill all of the lawyers responsible.
By comparison, your car's engine is about 25% more fuel-efficient, can produce 50-100% more power per unit of displacement thanks to its higher speed, is liquid-cooled, is often variably-timed, will run on unleaded low-octane fuel, and is probably much quieter than an aircraft engine.
Many automotive engines, from Honda Goldwing engines to Chevy 350 cu. in. V8's and on up, are converted to air use in Experimental Aviation. They usually must be geared down to swing a decent-sized prop at a reasonable mach number (supersonic prop tips are bad). Some pilots do this because of the costs of a certified engine ($20k+, plus regular maintenance by an A&P), some do it because 100LL avgas is so expensive, some do it because they believe the end result will be more trustworthy.
As for rotaries, yes, they'll save you a bunch on weight (and size, if needed), and some people put them in experimental aircraft. They have very few moving parts which increases reliability. Unfortunately the combustion chamber in a rotary has so much more surface area (per unit of displacement) than the equivalent reciprocal engine that rotaries will probably continue to lag 15-20% behind reciprocal engines on fuel efficiency.
HTTP requires one free port.
special firewall tuning
HTTP is extremely easy to pass through a firewall.
works through a layer of encryption without problems
HTTP over SSL is very commonly used.
but still doesn't generate a lot of overhead.
HTTP only adds perhaps a kilobyte to the transfer and requires very little CPU overhead.
In addition to this, HTTP supports resuming, content types, proxies, and is not tied to any particular authentication scheme.
Perhaps most importantly, HTTP is very widespread, widely understood, and proven.
The irony of you barely reading my post and then accusing me of not putting in the effort is truly touching.