magnetic field

Tim,

Check out the site www.shuroo.com. Look at the StrayBan product. Works
on many other animals. Should work on squirrels too.

Peter

================
Bear Electronics
www.bearelectronics.com.au
 
Clive Mitchell wrote:
In message <ffS8f.1284$zb5.1057@bgtnsc04-news.ops.worldnet.att.net>,
Steve TR <noemail@all.com> writes

I'm willing to spend $$$ for this project so I can get a correct look
and it seems a flat panel filling the entire area behind the lense
will work wonderfully. Aside from someone's time, I wouldn' think it
would be all that expensive... You can buy generic blank PCBs and a
box of LEDs and solder away. I just suck at soldering. LOL


OK, here's how you do it.

You take the lens dimensions and create a PCB outline to fit using a PCB
CAD program. You then populate the entire area with the pads required
for the LEDs and matching series resistors, and connect the pads with
tracks to make series multiples of four LEDs and a resistor per circuit
across common power bus tracks. Remember to allow for fixings to fit
the final PCB into the lens or base, and allow a couple of big pads for
attaching the connection wires. If you have multiple circuits then the
LEDs can be wired in clusters, possibly with diodes to allow individual
or multiple groups to be used from a common switch line.

Now print the finished PCB artwork onto a transparent or translucent
medium and expose a piece of photo sensitive PCB material in a suitable
UV exposure unit. The PCB can then be developed in an alkaline
developer based on Sodium Hydroxide, then rinsed and etched in a hot
bath of Ferric Chloride with air being blown through it to cause
circulation and agitation of the etchant. Once etched you can then hand
drill the several hundred 1mm holes required for the components with a
small hand-held drill and then crop the PCB to size and shape before
mounting the resistors on the back, cropping the leads at the front and
then populating the entire front surface with high output (635nm?) LEDs.
If using superflux these are pretty good at self levelling, but 5mm LEDs
are best having their anodes soldered first then hand levelled
individually before having the cathodes soldered. The choice of
resistor value can be calculated as 13.8 - (4*LED-Vf) / LED-I (20mA for
5mm or 50mA for superflux). You can calculate the appropriate power
rating for the resistors by multiplying the voltage dropped across them
by the current and rounding up to the nearest power rating.

Now simply pop into your lens and bingo, there you go.

Seems like it'd be FAR easier for the novice to use perfboard, at least
for the prototype, then if a PCB is designed use one of the online board
houses that will professionally make the PCBs, the end product is far
nicer for a lot less effort.
 
On 2005-10-27, Richard <richard_s633@cox.net> wrote:
"Pat" <pat@usenet-only.com> wrote in message
news:4360ff69$0$49798$ed2e19e4@ptn-nntp-reader04.plus.net...
http://www.tvsoundregulator.com/index.html

It seems a bit too good to be true (like those aerials you glue inside
your cellphone?)
Anyone any experience of these?
Are there other brands?
Should it be cheaper?

I never learned that the audio was part of the
composite video; part of the RF signal, yes. If they are separately messing
with the left and right channels ("for true stereo sound"), they will likely
screw up real stereo sound. I am real glad the response time is fast enough
for the really fast listeners - 2 microseconds!
when you demodulste antenna signal you out the baseband video signal
and the sound signal FM modulated a few MHZ (precice value differing with
different video standards)

NICAM otoh is transmitted in the video band during the horiozontal blanking
period...

I'd be willing to bet it doesn't works nearly as well as the site states.
However, if they want to send you one to review (for free, of course), the
unbiased opinion of someone who has actually used one would be nice.
once the advertisers figure out how it works they'll find a way to defeat it.

Bye.
Jasen
 
<googlinggoogler@hotmail.com> wrote in message
news:1130666161.622729.90770@g47g2000cwa.googlegroups.com...

how would I then take my power off the battery to my
electronics, Becuase if i draw off say 5v through a regulator would I
need to have increase the voltage that I charge my battery at to keep
it constantly charged?
No. Lead Acid batteries need a constant voltage charger. Just leave the
float charger connected. It will automatically supply the extra _current_
needed to compensate for the current drawn by your circuit. However the
charger must be rated for that current. eg If you want to draw 7A from the
battery continuously you need a charger that can supply at least say 8A.
That's 7A to power your circuit and 1A to charge the battery. I have a cheap
float charger that can supply about 3A no problem.
 
In article <1130621105.206554.233800@g14g2000cwa.googlegroups.com>,
"Bret Ludwig" <bretldwig@yahoo.com> wrote:

Spending large sums of money for textbooks for EE is a scam because
classical EE is an old discipline and it could be taught perfectly
using mostly booke now out of copyright from old age or from government
free use texts like Navy rate training manuals.

They pay professors enough, they should be prohibited from writing
textbooks and then making them mandatory.
Buy your books online. A lot of those companies reimport from overseas
where the exact same textbooks are sold at 33-50% of the US retail price.

half.com is a good place...I saved well over a thousand dollars by using
that the last two years of college.

--
|\/| /| |2 |<
mehaase(at)gmail(dot)com
 
JeffM wrote:

http://www.tvsoundregulator.com/index.html
It seems a bit too good to be true
(like those aerials you glue inside your cellphone?)
Pat


Automatic Gain Control (compression) is nothing new.

With modular entertainment systems becoming more popular,
this seems like a natural offering.
It appears to go between the TV and an external sound system
and you mute the speaker in the TV.

The specifications are bulls**t, The response time of 2 uS is
ridiculous for a frequency response down to 20 Hz! I wonder if its even
got any active circuit in it. It doesn't mention ANYTHING about a power
supply or battery. If it hasn't got one, then the only approch I can
imagine actually working is a LED driven off the signal illuminating an
ORP12 in an attenuator circuit.

If you want an interesting project, Sample the sound output with a
microphone at the speaker. compare with your desired level and generate
Vol + or Vol - signals to send to the TV via an IR LED.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
*Warning* SPAM TRAP set in header, Use email address in sig. if you must.
 
Chris Jones wrote:

Better to use a low-dropout regulator rather than the LM317, otherwise
you'll waste a good fraction of your hard-won solar power in the regulator.
Even better to use a shunt regulator: no voltage loss.


Thomas
 
<googlinggoogler@hotmail.com> wrote in message
news:1130666161.622729.90770@g47g2000cwa.googlegroups.com...
Hiya,

I wish to design a system that will be connected to the mains and will
charge a battery (small 12v battery) that will continue to supply power
even if the mains goes off (A.K.A. - powercut)

So i figure I can just use a simple charger
(http://www.durhambats.org.uk/batlight.htm), that constantly charges
the battery. But my question is, how effective is this, would it damage
the battery,
Use a charger that has a Float/Full switch. The float setting is designed
for permanant charging (eg months). On the float setting the voltage is
reduced to around 13.5V to prevent the battery "boiling" and loosing
electrolyte. On the float setting all you need do is check the fluid levels
every few months.

That article you linked to mentions this briefly... It says....

"Battery manufacturers recommend charging at a charge voltage of 13.5 -
13.8V for standby, and 14.4 v - 15v for cyclic (charging and discharging) -
but if using the latter, which gives a faster charge, you must turn it off
when fully charged. I use the 13.8V option, and leave my battery charging
until I need it"
 
On 30 Oct 2005 01:56:01 -0800, googlinggoogler@hotmail.com wrote:

Hiya,

I wish to design a system that will be connected to the mains and will
charge a battery (small 12v battery) that will continue to supply power
even if the mains goes off (A.K.A. - powercut)

So i figure I can just use a simple charger
(http://www.durhambats.org.uk/batlight.htm), that constantly charges
the battery. But my question is, how effective is this, would it damage
the battery, and how would I then take my power off the battery to my
electronics, Becuase if i draw off say 5v through a regulator would I
need to have increase the voltage that I charge my battery at to keep
it constantly charged?

Yours Gratefully

David
If your "small" battery is matched to the charger (can't overheat the
battery by trying to charge too fast) you should be goood to go.

Your regulator has nothing to do with the charger. You'll get 5V as
long as the battery has 9 volts to supply (or 6 volts with a low drop
out regulator)

Your regulator provides 5 volts to your electronics. Your battery is
out ther doing its best to maintain 12+ volts. You don't need to
worry about the charge - the battery charger takes care of that part.

you do have a battery charger?

We use things like "battery disconnect" circuits that disconnect the
battery, lest it be discharged too low and destroyed . . .(applies to
lead-acid batteries - but not capacitors and most NiMH, some NiCads,
etc..)

Many batteries can be damaged by discharging them "too low"



----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
 
"Bret Ludwig" <bretldwig@yahoo.com> wrote in message
news:1130621105.206554.233800@g14g2000cwa.googlegroups.com...
Spending large sums of money for textbooks for EE is a scam because
classical EE is an old discipline and it could be taught perfectly
using mostly booke now out of copyright from old age or from government
free use texts like Navy rate training manuals.

They pay professors enough, they should be prohibited from writing
textbooks and then making them mandatory
Why don't you share with friends or borrow from the library and make notes
from the material?
 
"Steven O." <null@null.com> wrote in message
news:pe1bm1tt9q0elp1c7lmlr1hr1sqsgmdmrn@4ax.com...
This is a repost, because I am having an unbelievably difficult time
tracking down a community college which offers the EE class I want on
a distance learning basis. I'm hoping maybe someone -- someone who
can point me in the right direction -- might catch the post this time,
if they missed it the first time.....

I am seeking information on any community colleges, anywhere in the
USA, that provide distance-learning (that is, Web-based, CD-based,
self-paced textbook study, etc.), for-credit programs of study in
electronic engineering. I really need community college based
classes, because costs are an issue. (The community colleges in
Maryland, where I am based, do NOT offer such classes, and UMUC does
not either. The nearest community college in Virginia does offer such
classes, but I have run through their distance learning course
offerings.)

I have already completed studies in basics of circuits and digital
design, but now need classes in transistor theory, basic analog
circuits (amplifiers, op-amps, oscillators, etc.) Please reply in the
newsgroups, or to the somewhat munged e-mail address below.

I've searched the Web extensively, and it's becoming clear that many
colleges -- even technically oriented community colleges, and ones
which have many other programs of study online -- are not offering EE
programs. I've love to know why. (I thought, maybe, it's because EE
classes often have labs. But in fact, you can have theory only EE
classes; and besides, many of these same schools offer
freshman/sophomore distance learning classes in chemistry, biology,
and physics -- fields which traditionally also have labs as well.)
Taking engineering courses without doing lab work produces engineers who
don't know which end of a soldering iron gets hot or which end of the
adjustable wrench should be used to pound the ICs into their sockets. That
is probably the one that said, "Spectrum analyzer? Yeah, I saw a picture of
one of those in one of my books, I think."

I have found, so far, exactly one college offering what I'm seeking,
Sinclair Community College in Ohio -- but for various reasons, too
detailed to go into here, their course is probably less than ideal for
my needs. So, I'm searching for other community colleges offering the
class that I'm seeking, distance learning style. Direct leads from
people in the know -- students and engineers -- would be really
helpful.
Okay, it looks like you have been unable to meet your criteria through
online searches. You may never meet all your requirements (for credit,
distance learning, ee courses, low cost). One avenue you may want to explore
is to talk with the professors at the colleges/universities that meet your
course offering and cost criteria. You may be able to work out a modified
schedule with them (some have more leeway to make the attendance decision
than others), so you can do the majority of your work outside of the
classroom (you will still have to show up for tests and labs). Assuming they
have the authority, if you can prove to them that you have the capability to
work independently and have a very good (legitimate) reason to not attend
all classes, they may be willing to work with you.. I have taken many
courses this way (I was also in my 40's and 50's and had a job that required
me to travel). Of course, many colleges have official policies limiting the
number of days a student can miss and some do not allow their professors to
waive this. Others are more flexible.

If you want to attend NO classes, you may, as you have discovered, be out of
luck.

One last suggestion: For the cost issue, check out scholarships, grants, and
financial aid. You can't get any of those if you don't apply. They may make
the difference that will allow you to take available university courses at
nearly the same out-of-pocket costs as the (non-existent) community college
courses.

Richard
 
The numbers on the packages are meaningless. They're house
numbers. The color code will give you the part number. It's
just like the resistor color code.

sreenath wrote:
Hi all,

A few years ago (1995) I bought a scoop of plastic transistors from
a company called "electronic goldmine". I am unable to get any data
on these transistors.

Can anyone please identify these transistors?

All are plastic, small signal packages, I think to-92 type.

1. national semiconductor. marking "615-3"

2. national semiconductor. marking "2553"

3. national semiconductor. marking "435-1"

In addition, all of these also have another number like "827",
"826", but I think they are the year of marking and month/quarter,
etc. Apart from these two, there is nothing else printed on the
device.

Curioucly, there is a three color band coding on the back of the
device,
I dnot know if this indicated a current gain factor or something.
 
Yes, but that's a separate problem. EE is one of the areas where
I think textbook revisions are useful. You could probably convince
me that calculus doesn't change all that much. The basic theory
textbooks are a very small part of the whole package.

Mike W. wrote:
Well when you have to come up with $500 a quarter (or semester, whatever)
for books that you can't sell back, it gets a little rediculous.
 
The University of Illinois offers distance learning classes and
they take a lot of time and effort on the part of the professors
and teachers. They may be more convenient for the student, but
require more one-to-one contact from the faculty than traditional
classes. They also require development of new materials, since
you can't always adapt traditional classroom methods. It's
expensive and time consuming to develop and offer those courses.

Steven O. wrote:
This is a repost, because I am having an unbelievably difficult time
tracking down a community college which offers the EE class I want on
a distance learning basis. I'm hoping maybe someone -- someone who
can point me in the right direction -- might catch the post this time,
if they missed it the first time.....
....
I have found, so far, exactly one college offering what I'm seeking,
Sinclair Community College in Ohio -- but for various reasons, too
detailed to go into here, their course is probably less than ideal for
my needs. So, I'm searching for other community colleges offering the
class that I'm seeking, distance learning style. Direct leads from
people in the know -- students and engineers -- would be really
helpful.
 
"Bret Ludwig" <bretldwig@yahoo.com> wrote in message
news:1130621105.206554.233800@g14g2000cwa.googlegroups.com...
Spending large sums of money for textbooks for EE is a scam because
classical EE is an old discipline and it could be taught perfectly
using mostly booke now out of copyright from old age or from government
free use texts like Navy rate training manuals.
NAVPERS manuals are simply great (for technicians):
http://www.tscm.com/NEETS-v13-Logic.pdf No reason why engineering
students cannot use them ... but they are somewhat lacking in theory and
math.

They pay professors enough, they should be prohibited from writing
textbooks and then making them mandatory.
I taught EET at universities for 33 years and chose to write textbooks and
consult to be able to feed a family of four and live in a decent home and
drive a decent car and afford dental care (not provided by my employer) and
send my kids to college. Point of view is everything! My book royalties
and consulting income exceeded my salary for 15 of those years.

I absolutely agree about the mandatory part! That sucks and should not be
allowed.
 
You seem to need the basic "linear electronic" course (also sometimes called
electronic devices) as so named by many community colleges. It covers
diodes, power supplies, transistors, amplifiers, oscillators, op-amps, and
so on. Its a tough course to offer on-line. It requires hands-on lab work
to make the ideas sink in and take hold.
 
On Mon, 31 Oct 2005 10:54:04 -0500, "Richard" <richard_s633@cox.net>
wrote:
Taking engineering courses without doing lab work produces engineers who
don't know which end of a soldering iron gets hot or which end of the
adjustable wrench should be used to pound the ICs into their sockets. That
is probably the one that said, "Spectrum analyzer? Yeah, I saw a picture of
one of those in one of my books, I think."
That may be true, but not everyone takes classes for the same reason.
In my case, I am an experienced technical writer, and recently
licensed patent agent, looking to get a stronger background for my
work. (Check out www.OpComm.com for more info....)

I don't doubt that, with distance-learning only, I may not be
qualified to invent the next generation of computer, or holographic
TV, or whatever. But, I don't need to be, I just need a good strong
vocabulary for working with the engineers who do invent this stuff.
Many others -- software guys who want to understand the hardware
better, hi-tech business managers, hi-tech investors, etc. -- may have
their own valid motives for wanting to delve deep into theory, without
having the need (or time) to do lab work. Not to mention, there is
always the simple pleasure of learning for the sake of learning. My
point is, there are plenty of valid reasons for offering EE courses
without labs, since not everyone plans to be a design engineer.

One last suggestion: For the cost issue, check out scholarships, grants, and
financial aid. You can't get any of those if you don't apply. They may make
That's a whole nother discussion. Those are great for young people
making no money at all. If you have an income like I do, even if the
budget is tight, forget about scholarships. Someone should fund some
kind of "second chance" grants for adults who are returning to pursue
things they were not ready to do when younger. (I actually seached on
the Web for "second chance", and found a scholarship, but it's for
women only, and I think it was, something like, only women in
California. So if I just move cross country, and finally get that
operation done.....)

Steve O.

"Steven O." <null@null.com> wrote in message
news:pe1bm1tt9q0elp1c7lmlr1hr1sqsgmdmrn@4ax.com...
This is a repost, because I am having an unbelievably difficult time
tracking down a community college which offers the EE class I want on
a distance learning basis. I'm hoping maybe someone -- someone who
can point me in the right direction -- might catch the post this time,
if they missed it the first time.....

I am seeking information on any community colleges, anywhere in the
USA, that provide distance-learning (that is, Web-based, CD-based,
self-paced textbook study, etc.), for-credit programs of study in
electronic engineering. I really need community college based
classes, because costs are an issue. (The community colleges in
Maryland, where I am based, do NOT offer such classes, and UMUC does
not either. The nearest community college in Virginia does offer such
classes, but I have run through their distance learning course
offerings.)

I have already completed studies in basics of circuits and digital
design, but now need classes in transistor theory, basic analog
circuits (amplifiers, op-amps, oscillators, etc.) Please reply in the
newsgroups, or to the somewhat munged e-mail address below.

I've searched the Web extensively, and it's becoming clear that many
colleges -- even technically oriented community colleges, and ones
which have many other programs of study online -- are not offering EE
programs. I've love to know why. (I thought, maybe, it's because EE
classes often have labs. But in fact, you can have theory only EE
classes; and besides, many of these same schools offer
freshman/sophomore distance learning classes in chemistry, biology,
and physics -- fields which traditionally also have labs as well.)

Taking engineering courses without doing lab work produces engineers who
don't know which end of a soldering iron gets hot or which end of the
adjustable wrench should be used to pound the ICs into their sockets. That
is probably the one that said, "Spectrum analyzer? Yeah, I saw a picture of
one of those in one of my books, I think."


I have found, so far, exactly one college offering what I'm seeking,
Sinclair Community College in Ohio -- but for various reasons, too
detailed to go into here, their course is probably less than ideal for
my needs. So, I'm searching for other community colleges offering the
class that I'm seeking, distance learning style. Direct leads from
people in the know -- students and engineers -- would be really
helpful.

Okay, it looks like you have been unable to meet your criteria through
online searches. You may never meet all your requirements (for credit,
distance learning, ee courses, low cost). One avenue you may want to explore
is to talk with the professors at the colleges/universities that meet your
course offering and cost criteria. You may be able to work out a modified
schedule with them (some have more leeway to make the attendance decision
than others), so you can do the majority of your work outside of the
classroom (you will still have to show up for tests and labs). Assuming they
have the authority, if you can prove to them that you have the capability to
work independently and have a very good (legitimate) reason to not attend
all classes, they may be willing to work with you.. I have taken many
courses this way (I was also in my 40's and 50's and had a job that required
me to travel). Of course, many colleges have official policies limiting the
number of days a student can miss and some do not allow their professors to
waive this. Others are more flexible.

If you want to attend NO classes, you may, as you have discovered, be out of
luck.

One last suggestion: For the cost issue, check out scholarships, grants, and
financial aid. You can't get any of those if you don't apply. They may make
the difference that will allow you to take available university courses at
nearly the same out-of-pocket costs as the (non-existent) community college
courses.

Richard

"Spying On The College Of Your Choice" -- How to pick the college that is the Best Match for a high school student's needs.
www.SpyingOnTheCollegeOfYourChoice.com
 
On Sun, 30 Oct 2005 18:24:00 +0000, Chris Jones wrote:

Rich Grise wrote:
[...]
Just rectify and filter the 12V from the generator and use a 110V
inverter. You could probably build a 25-watt inverter in about the
space of a couple of packs of cigarettes.

Cheers!
Rich
This isn't a very efficient arrangement. One really appreciate how much
energy is wasted in a wall-wart or cheap inverter when one must generate
that power through one's own muscles.
I'm going to have to get to work on my recliner bike design - it has
a novel feature: a gearless gear shift. :) But the point would be that
you could kind of kick back and pedal, which just kinda intuitively seems
like it'd be less work than sitting on top of a conventional bicycle.
There might even be a way to couple hand movements into the drive mech,
since you'll be sitting still, watching TV. :)

Cheers!
Rich
 
Lots of ideas here, but I think ken o's comment, "I also omitted that
I need 550 volts to tun this baby," slipped under everybody's radar.


That's a pretty big hooker unless he has 440 VAC service or a step-up
transformer capable of transforming the full power demanded by the
motor plus reserve. In fact, while I strongly disagree with the
comment by another poster that 3-phase conversion at home is not
practical, doing it for a 550 volt motor may well be. ken o will
either have to provide a single-phase transformer to transform his
input power to the converter up so the DC bus in his VFD is high
enough to provide 550 volts AC out, or he will have to provide a
3-phase transformer between the converter and the motor.

The former is reasonably practical, depending upon power requirements.
In fact, the manufacturer of the VFD I installed in my garage about
25 years ago mandated that the input be supplied via a 5 KW isolation
transformer. Such a transformer can as easily be a step-up
transformer as the unity-ratio transformer that I installed.

The latter is very risky and/or expensive for a several reasons. (1)
You need a 3-phase transformer. (2) You are subjecting the
transformer to the high rise-time switching transients that can lead
to insulation breakdown unless its insulation is specifically
designed to withstand them. (3) You CAN NOT use a transformer on the
output of a VFD that could possibly be set to lower frequency than the
transformer is designed for. The transformer would saturate, leading
to very large currents damaging either (or both) the VFD or the
transformer.

I have been using a solid-state VFD to drive my 3-phase geared-head
drilling machine, bench grinder, and Bridgeport milling machine with
complete satisfaction for more than two decades. Before I installed
the VFD, I changed the motor on my first milling machine (a Rockwell)
to single-phase. It worked fine, but changing the motor on the
Bridgeport was not an option, and the variable speed of the VFD is
extremely valuable, especially for drilling large holes with the
drilling machine. No more burned drills!

Ignoring the high voltage ken o requires, I strongly recommend
investing in a VFD instead of buying or building a rotary converter,
primarily to get the variable speed capability. I think that careful
shopping and not going for bells and whistles like an LCD readout or
programmability will get you a VFD good for up to about a 1 HP motor
for well below US$ 100.

The threat of a VFD to motors not designed for "Inverter Duty," is
from the fast transients from the IGBTs or MOSFETs. A couple of
things can happen. One is insulation punch-through. An equally
damaging, but less obvious phenomenon is capacitively-coupled current
spikes through the ball bearings leading to erosion of the balls and
races and ultimate failure. This is not an academic issue to me, as
the electronically controlled motor in my new, high-efficiency
clothes washing machine failed in less than a year. A post-mortem
clearly revealed severe bearing erosion. In replacing the motor, I
lifted the motor ground to interrupt the path for
capacitively-coupled transients to ground via the motor bearings. No
subsequent failures for 5 years. (I know that this is a serious
violation of safety codes, but the motor is fully enclosed and I hung
BIG warning sign on it explaining exactly what had been done. )

awright
 
Hi,
thanks for the tips. I tried using the color codes,and could not find
meaningful results.

There are three colors on the back of the transistor. Also, after I
don't have any way of knowing what the preceding type would be, like
2N, MPS, 2SC, etc.

I am really consufed. Don't know why a company like National
semiconductors does like this- not printing the full device type on the
transistor.

thanks,
Sreenath


Mike Berger wrote:
The numbers on the packages are meaningless. They're house
numbers. The color code will give you the part number. It's
just like the resistor color code.

sreenath wrote:
Hi all,

A few years ago (1995) I bought a scoop of plastic transistors from
a company called "electronic goldmine". I am unable to get any data
on these transistors.

Can anyone please identify these transistors?

All are plastic, small signal packages, I think to-92 type.

1. national semiconductor. marking "615-3"

2. national semiconductor. marking "2553"

3. national semiconductor. marking "435-1"

In addition, all of these also have another number like "827",
"826", but I think they are the year of marking and month/quarter,
etc. Apart from these two, there is nothing else printed on the
device.

Curioucly, there is a three color band coding on the back of the
device,
I dnot know if this indicated a current gain factor or something.
 

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