On Thursday, December 3, 2015 at 1:42:36 AM UTC-5, Robert Baer wrote:> Phil Hobbs wrote: > > On 12/01/2015 10:18 AM, piglet wrote: > >> On 01/12/2015 14:05, Phil Hobbs wrote: > >>> The switch and meter movement are pretty nice, so even if you can't > >>> get replacement MOSFETs, you could do a brain transplant with > >>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. > >>> > >>> Cheers > >>> > >>> Phil Hobbs > >>> > >> > >> If you search back postings in this NG a year or two ago John Larkin > >> posted schematic and photos of a box he built around an LMC6001 which do > >> pretty much the same job as the 610C for femto/pico ampere sleuthing. > >> > >> piglet > >> > > > > I think it was the same discussion where I was talking about using a > > charge dispensing loop with a 100-pF Teflon cap to do the same sort of > > thing. It's easier without resistors. > > > > Voltage measurement is pretty easy--you can make a follower and measure > > its output with a normal DVM. > > > > I have a couple of dozen MOSFETs without gate protection, and you can > > still get 2N7002Es, some of which leak only a few electrons per second. > > > > Cheers > > > > Phil Hobbs > > > ...which brings up a question: can one count the electrons (like > Millikan oil drop bit)?One way to measure the charge of the electron is by measuring the shot noise. (and the DC current) George H.
Keithley 610C repair
Started by ●December 1, 2015
Reply by ●December 3, 20152015-12-03
Reply by ●December 3, 20152015-12-03
On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer <robertbaer@localnet.com> wrote:>Phil Hobbs wrote: >> On 12/01/2015 10:18 AM, piglet wrote: >>> On 01/12/2015 14:05, Phil Hobbs wrote: >>>> The switch and meter movement are pretty nice, so even if you can't >>>> get replacement MOSFETs, you could do a brain transplant with >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>>> >>> >>> If you search back postings in this NG a year or two ago John Larkin >>> posted schematic and photos of a box he built around an LMC6001 which do >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. >>> >>> piglet >>> >> >> I think it was the same discussion where I was talking about using a >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of >> thing. It's easier without resistors. >> >> Voltage measurement is pretty easy--you can make a follower and measure >> its output with a normal DVM. >> >> I have a couple of dozen MOSFETs without gate protection, and you can >> still get 2N7002Es, some of which leak only a few electrons per second. >> >> Cheers >> >> Phil Hobbs >> >...which brings up a question: can one count the electrons (like >Millikan oil drop bit)?I've thought that some simple semiconductor experiment could demonstrate charge quantization. It would make a nice science project. The numbers are intimidating but maybe not impossible. You might not see single electrons, but could dig out something statistically. An eprom is a possible detector. Or maybe a cmos imager.
Reply by ●December 3, 20152015-12-03
On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote:> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer > <robertbaer@localnet.com> wrote: > > >Phil Hobbs wrote: > >> On 12/01/2015 10:18 AM, piglet wrote: > >>> On 01/12/2015 14:05, Phil Hobbs wrote: > >>>> The switch and meter movement are pretty nice, so even if you can't > >>>> get replacement MOSFETs, you could do a brain transplant with > >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. > >>>> > >>>> Cheers > >>>> > >>>> Phil Hobbs > >>>> > >>> > >>> If you search back postings in this NG a year or two ago John Larkin > >>> posted schematic and photos of a box he built around an LMC6001 which do > >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. > >>> > >>> piglet > >>> > >> > >> I think it was the same discussion where I was talking about using a > >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of > >> thing. It's easier without resistors. > >> > >> Voltage measurement is pretty easy--you can make a follower and measure > >> its output with a normal DVM. > >> > >> I have a couple of dozen MOSFETs without gate protection, and you can > >> still get 2N7002Es, some of which leak only a few electrons per second. > >> > >> Cheers > >> > >> Phil Hobbs > >> > >...which brings up a question: can one count the electrons (like > >Millikan oil drop bit)? > > I've thought that some simple semiconductor experiment could > demonstrate charge quantization. It would make a nice science project. > > The numbers are intimidating but maybe not impossible. You might not > see single electrons, but could dig out something statistically. > > An eprom is a possible detector. Or maybe a cmos imager.What are you thinking? Charge quantization.. things. Shot noise. SPAD's sorta start out as a single electron... like pulse counting in a pmt. Quantum conductance. (You can see steps in the resistance of two thin gold wires that are intermittently touching each other.) George H.
Reply by ●December 3, 20152015-12-03
George Herold <gherold@teachspin.com> writes:> On Tuesday, December 1, 2015 at 10:17:47 AM UTC-5, piglet wrote: >> On 01/12/2015 14:05, Phil Hobbs wrote: >> > The switch and meter movement are pretty nice, so even if you >> > can't get replacement MOSFETs, you could do a brain transplant >> > with something like an LMC662 or 6001 and have a fairly swoopy >> > gizmo. >> > >> > Cheers >> > >> > Phil Hobbs >> > >> >> If you search back postings in this NG a year or two ago John Larkin >> posted schematic and photos of a box he built around an LMC6001 which do >> pretty much the same job as the 610C for femto/pico ampere sleuthing. >> >> piglet > > Yeah I might think about building my own too. I've measured pA with a > "leaky" Fet opamp. The LMC662 looks nice also (as Phil noted.) And it's > a lot cheaper... you could blow up a few for ~$1.5 each.That is what is in a 6517 anyway! -- John Devereux
Reply by ●December 3, 20152015-12-03
On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer >> <robertbaer@localnet.com> wrote: >> >> >Phil Hobbs wrote: >> >> On 12/01/2015 10:18 AM, piglet wrote: >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: >> >>>> The switch and meter movement are pretty nice, so even if you can't >> >>>> get replacement MOSFETs, you could do a brain transplant with >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. >> >>>> >> >>>> Cheers >> >>>> >> >>>> Phil Hobbs >> >>>> >> >>> >> >>> If you search back postings in this NG a year or two ago John Larkin >> >>> posted schematic and photos of a box he built around an LMC6001 which do >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. >> >>> >> >>> piglet >> >>> >> >> >> >> I think it was the same discussion where I was talking about using a >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of >> >> thing. It's easier without resistors. >> >> >> >> Voltage measurement is pretty easy--you can make a follower and measure >> >> its output with a normal DVM. >> >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can >> >> still get 2N7002Es, some of which leak only a few electrons per second. >> >> >> >> Cheers >> >> >> >> Phil Hobbs >> >> >> >...which brings up a question: can one count the electrons (like >> >Millikan oil drop bit)? >> >> I've thought that some simple semiconductor experiment could >> demonstrate charge quantization. It would make a nice science project. >> >> The numbers are intimidating but maybe not impossible. You might not >> see single electrons, but could dig out something statistically. >> >> An eprom is a possible detector. Or maybe a cmos imager. > >What are you thinking? >Charge quantization.. things. > >Shot noise.That's not as appealing as seeing single-electron steps. Some day I may try the eprom thing.>SPAD's sorta start out as a single electron... like pulse counting in a pmt. >Quantum conductance. (You can see steps in the resistance of two >thin gold wires that are intermittently touching each other.) > >George H.-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 4, 20152015-12-04
On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote:> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: > >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer > >> <robertbaer@localnet.com> wrote: > >> > >> >Phil Hobbs wrote: > >> >> On 12/01/2015 10:18 AM, piglet wrote: > >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: > >> >>>> The switch and meter movement are pretty nice, so even if you can't > >> >>>> get replacement MOSFETs, you could do a brain transplant with > >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. > >> >>>> > >> >>>> Cheers > >> >>>> > >> >>>> Phil Hobbs > >> >>>> > >> >>> > >> >>> If you search back postings in this NG a year or two ago John Larkin > >> >>> posted schematic and photos of a box he built around an LMC6001 which do > >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. > >> >>> > >> >>> piglet > >> >>> > >> >> > >> >> I think it was the same discussion where I was talking about using a > >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of > >> >> thing. It's easier without resistors. > >> >> > >> >> Voltage measurement is pretty easy--you can make a follower and measure > >> >> its output with a normal DVM. > >> >> > >> >> I have a couple of dozen MOSFETs without gate protection, and you can > >> >> still get 2N7002Es, some of which leak only a few electrons per second. > >> >> > >> >> Cheers > >> >> > >> >> Phil Hobbs > >> >> > >> >...which brings up a question: can one count the electrons (like > >> >Millikan oil drop bit)? > >> > >> I've thought that some simple semiconductor experiment could > >> demonstrate charge quantization. It would make a nice science project. > >> > >> The numbers are intimidating but maybe not impossible. You might not > >> see single electrons, but could dig out something statistically. > >> > >> An eprom is a possible detector. Or maybe a cmos imager. > > > >What are you thinking? > >Charge quantization.. things. > > > >Shot noise. > > That's not as appealing as seeing single-electron steps. Some day I > may try the eprom thing.I don't know eproms that well... what are you going to see? The bouncing gold wires/ quantum conductance thing is sorta single electron. The contact area is so small that there can be only one electron state in it. A box so small it can only hold one particle. (really two electrons 'cause of spin) Here is some old data... circa 1995.. Yellowing dot matrix printer paper. https://www.dropbox.com/s/x4hspn16olrtnix/DSCN0247.JPG?dl=0 https://www.dropbox.com/s/wis8di109ppmt4e/DSCN0248.JPG?dl=0 Constant voltage source across the wires and the Y-axis is the current. In theory each step should be 12.7 k ohms... or something near to that. George H.> > > > >SPAD's sorta start out as a single electron... like pulse counting in a pmt. > >Quantum conductance. (You can see steps in the resistance of two > >thin gold wires that are intermittently touching each other.) > > > >George H. > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
Reply by ●December 4, 20152015-12-04
On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: >> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: >> >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer >> >> <robertbaer@localnet.com> wrote: >> >> >> >> >Phil Hobbs wrote: >> >> >> On 12/01/2015 10:18 AM, piglet wrote: >> >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: >> >> >>>> The switch and meter movement are pretty nice, so even if you can't >> >> >>>> get replacement MOSFETs, you could do a brain transplant with >> >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. >> >> >>>> >> >> >>>> Cheers >> >> >>>> >> >> >>>> Phil Hobbs >> >> >>>> >> >> >>> >> >> >>> If you search back postings in this NG a year or two ago John Larkin >> >> >>> posted schematic and photos of a box he built around an LMC6001 which do >> >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. >> >> >>> >> >> >>> piglet >> >> >>> >> >> >> >> >> >> I think it was the same discussion where I was talking about using a >> >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of >> >> >> thing. It's easier without resistors. >> >> >> >> >> >> Voltage measurement is pretty easy--you can make a follower and measure >> >> >> its output with a normal DVM. >> >> >> >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can >> >> >> still get 2N7002Es, some of which leak only a few electrons per second. >> >> >> >> >> >> Cheers >> >> >> >> >> >> Phil Hobbs >> >> >> >> >> >...which brings up a question: can one count the electrons (like >> >> >Millikan oil drop bit)? >> >> >> >> I've thought that some simple semiconductor experiment could >> >> demonstrate charge quantization. It would make a nice science project. >> >> >> >> The numbers are intimidating but maybe not impossible. You might not >> >> see single electrons, but could dig out something statistically. >> >> >> >> An eprom is a possible detector. Or maybe a cmos imager. >> > >> >What are you thinking? >> >Charge quantization.. things. >> > >> >Shot noise. >> >> That's not as appealing as seeing single-electron steps. Some day I >> may try the eprom thing. > >I don't know eproms that well... what are you going to see?The charge stored in an eprom cell is fC. And it's accessable to UV to discharge it. The idea would be to scan an eprom and snoop the cell contents. Modulate Vcc and apply UV, and look for bits that are marginal, namely toggling 1/0 as Vcc changes slightly. That will plot as a step function. Now apply some UV; maybe absorbing one UV photon will cause one (or possibly more) electrons worth of discharge, which would make a horizontal jump on the plot. Multiple jumps should be quantized to the value of e. It might be possible to detect electron charge steps in a discrete fet of some sort, but the capacitance involved will be hundreds of times the capacitance of an eprom (or ram, or CCD) cell. One electron charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is some statistical way to tease 400 nV random steps out of a lot of noise. There may be some other IC that has an internal floating node that has very low capacitance and can be accessed somehow. I should do the math on LTC6268-10; not right now.
Reply by ●December 4, 20152015-12-04
On Friday, December 4, 2015 at 12:40:01 PM UTC-5, John Larkin wrote:> On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: > >> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: > >> >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer > >> >> <robertbaer@localnet.com> wrote: > >> >> > >> >> >Phil Hobbs wrote: > >> >> >> On 12/01/2015 10:18 AM, piglet wrote: > >> >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: > >> >> >>>> The switch and meter movement are pretty nice, so even if you can't > >> >> >>>> get replacement MOSFETs, you could do a brain transplant with > >> >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. > >> >> >>>> > >> >> >>>> Cheers > >> >> >>>> > >> >> >>>> Phil Hobbs > >> >> >>>> > >> >> >>> > >> >> >>> If you search back postings in this NG a year or two ago John Larkin > >> >> >>> posted schematic and photos of a box he built around an LMC6001 which do > >> >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. > >> >> >>> > >> >> >>> piglet > >> >> >>> > >> >> >> > >> >> >> I think it was the same discussion where I was talking about using a > >> >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of > >> >> >> thing. It's easier without resistors. > >> >> >> > >> >> >> Voltage measurement is pretty easy--you can make a follower and measure > >> >> >> its output with a normal DVM. > >> >> >> > >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can > >> >> >> still get 2N7002Es, some of which leak only a few electrons per second. > >> >> >> > >> >> >> Cheers > >> >> >> > >> >> >> Phil Hobbs > >> >> >> > >> >> >...which brings up a question: can one count the electrons (like > >> >> >Millikan oil drop bit)? > >> >> > >> >> I've thought that some simple semiconductor experiment could > >> >> demonstrate charge quantization. It would make a nice science project. > >> >> > >> >> The numbers are intimidating but maybe not impossible. You might not > >> >> see single electrons, but could dig out something statistically. > >> >> > >> >> An eprom is a possible detector. Or maybe a cmos imager. > >> > > >> >What are you thinking? > >> >Charge quantization.. things. > >> > > >> >Shot noise. > >> > >> That's not as appealing as seeing single-electron steps. Some day I > >> may try the eprom thing. > > > >I don't know eproms that well... what are you going to see? > > > The charge stored in an eprom cell is fC. And it's accessable to UV to > discharge it. > > The idea would be to scan an eprom and snoop the cell contents. > Modulate Vcc and apply UV, and look for bits that are marginal, namely > toggling 1/0 as Vcc changes slightly. That will plot as a step > function. Now apply some UV; maybe absorbing one UV photon will cause > one (or possibly more) electrons worth of discharge, which would make > a horizontal jump on the plot. Multiple jumps should be quantized to > the value of e. > > It might be possible to detect electron charge steps in a discrete fet > of some sort, but the capacitance involved will be hundreds of times > the capacitance of an eprom (or ram, or CCD) cell. One electron > charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is > some statistical way to tease 400 nV random steps out of a lot of > noise.Well some synchronous, lockin type detection. ramping a current back and forth into a cap and seeing voltage steps would be awesome. Currents from a voltage source through a resistor have no shot noise.. which I think means the electrons are coming at you in a well ordered train.... hmm I guess there is no guarantee that the first "train" of electrons and the next have any phase relationship.. steps are smeared into the expected ramp. Next idea please... (That's me talking to my brain, or God, or wherever ideas come from.) George H.> > There may be some other IC that has an internal floating node that has > very low capacitance and can be accessed somehow. > > I should do the math on LTC6268-10; not right now.
Reply by ●December 4, 20152015-12-04
On 04/12/2015 17:39, John Larkin wrote:> It might be possible to detect electron charge steps in a discrete fet > of some sort, but the capacitance involved will be hundreds of times > the capacitance of an eprom (or ram, or CCD) cell. One electron > charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is > some statistical way to tease 400 nV random steps out of a lot of > noise.I think it is less than 400nV. By V=Q/C I get Qe/1pF = 160nV piglet
Reply by ●December 4, 20152015-12-04
On Fri, 4 Dec 2015 10:06:21 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Friday, December 4, 2015 at 12:40:01 PM UTC-5, John Larkin wrote: >> On Fri, 4 Dec 2015 09:13:19 -0800 (PST), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Thursday, December 3, 2015 at 4:01:51 PM UTC-5, John Larkin wrote: >> >> On Thu, 3 Dec 2015 09:34:49 -0800 (PST), George Herold >> >> <gherold@teachspin.com> wrote: >> >> >> >> >On Thursday, December 3, 2015 at 11:44:31 AM UTC-5, John Larkin wrote: >> >> >> On Wed, 02 Dec 2015 22:42:32 -0800, Robert Baer >> >> >> <robertbaer@localnet.com> wrote: >> >> >> >> >> >> >Phil Hobbs wrote: >> >> >> >> On 12/01/2015 10:18 AM, piglet wrote: >> >> >> >>> On 01/12/2015 14:05, Phil Hobbs wrote: >> >> >> >>>> The switch and meter movement are pretty nice, so even if you can't >> >> >> >>>> get replacement MOSFETs, you could do a brain transplant with >> >> >> >>>> something like an LMC662 or 6001 and have a fairly swoopy gizmo. >> >> >> >>>> >> >> >> >>>> Cheers >> >> >> >>>> >> >> >> >>>> Phil Hobbs >> >> >> >>>> >> >> >> >>> >> >> >> >>> If you search back postings in this NG a year or two ago John Larkin >> >> >> >>> posted schematic and photos of a box he built around an LMC6001 which do >> >> >> >>> pretty much the same job as the 610C for femto/pico ampere sleuthing. >> >> >> >>> >> >> >> >>> piglet >> >> >> >>> >> >> >> >> >> >> >> >> I think it was the same discussion where I was talking about using a >> >> >> >> charge dispensing loop with a 100-pF Teflon cap to do the same sort of >> >> >> >> thing. It's easier without resistors. >> >> >> >> >> >> >> >> Voltage measurement is pretty easy--you can make a follower and measure >> >> >> >> its output with a normal DVM. >> >> >> >> >> >> >> >> I have a couple of dozen MOSFETs without gate protection, and you can >> >> >> >> still get 2N7002Es, some of which leak only a few electrons per second. >> >> >> >> >> >> >> >> Cheers >> >> >> >> >> >> >> >> Phil Hobbs >> >> >> >> >> >> >> >...which brings up a question: can one count the electrons (like >> >> >> >Millikan oil drop bit)? >> >> >> >> >> >> I've thought that some simple semiconductor experiment could >> >> >> demonstrate charge quantization. It would make a nice science project. >> >> >> >> >> >> The numbers are intimidating but maybe not impossible. You might not >> >> >> see single electrons, but could dig out something statistically. >> >> >> >> >> >> An eprom is a possible detector. Or maybe a cmos imager. >> >> > >> >> >What are you thinking? >> >> >Charge quantization.. things. >> >> > >> >> >Shot noise. >> >> >> >> That's not as appealing as seeing single-electron steps. Some day I >> >> may try the eprom thing. >> > >> >I don't know eproms that well... what are you going to see? >> >> >> The charge stored in an eprom cell is fC. And it's accessable to UV to >> discharge it. >> >> The idea would be to scan an eprom and snoop the cell contents. >> Modulate Vcc and apply UV, and look for bits that are marginal, namely >> toggling 1/0 as Vcc changes slightly. That will plot as a step >> function. Now apply some UV; maybe absorbing one UV photon will cause >> one (or possibly more) electrons worth of discharge, which would make >> a horizontal jump on the plot. Multiple jumps should be quantized to >> the value of e. >> >> It might be possible to detect electron charge steps in a discrete fet >> of some sort, but the capacitance involved will be hundreds of times >> the capacitance of an eprom (or ram, or CCD) cell. One electron >> charges 1 pF to 0.4 uV, which is intimidating. I wonder if there is >> some statistical way to tease 400 nV random steps out of a lot of >> noise. >Well some synchronous, lockin type detection.OK, mesure the transition point, make a UV blip, measure again, repeat.>ramping a current back and forth into a cap and seeing voltage steps >would be awesome. >Currents from a voltage source through a resistor have no shot noise.. >which I think means the electrons are coming at you in a well ordered >train.... hmm I guess there is no guarantee that the first "train" of >electrons and the next have any phase relationship.. steps are smeared >into the expected ramp.I expect that low currents have very small electron correlations, so shot noise returns. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
