How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Jim Thompson wrote:

How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

Google found this: http://www.tscm.com/phone/line_current.html

So it seems (according to unknown authorities posting on the Internets) that
the threshold is 18 mA. I didn't read through the entire thread. Someone
might have actually cited an authoritative source. A true first for the
Usenet, I'm sure. ;-)

--
Paul Hovnanian
----------------------------------------------------------------------
Have gnu, will travel.

Jim Thompson wrote:

How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

And then there's this: http://www.maxim-ic.com/app-notes/index.mvp/id/1923

--
Paul Hovnanian
----------------------------------------------------------------------
Have gnu, will travel.

On 03/01/2011 09:09 AM, Jim Thompson wrote:
How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

...Jim Thompson

CFR 47, part 68.312.b.1.i (1993 version -- you can look up the latest
yourself):

"The DC resistance between tip and ring conductors, and between each of
the tip and ring conductors and earth ground, shall be greater than 5
megohms for all DC voltages up to and including 100 volts."

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

"Tim Wescott" wrote in message
...
On 03/01/2011 09:09 AM, Jim Thompson wrote:
How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

...Jim Thompson

CFR 47, part 68.312.b.1.i (1993 version -- you can look up the latest
yourself):

"The DC resistance between tip and ring conductors, and between each of
the tip and ring conductors and earth ground, shall be greater than 5
megohms for all DC voltages up to and including 100 volts."

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html


Which is more in agreement with the less than 10uA *ON*hook current that I
recalled seeing in my errant youth when phone phreaking...

"Tim Wescott" wrote in message
...
On 03/01/2011 09:09 AM, Jim Thompson wrote:
How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

...Jim Thompson

CFR 47, part 68.312.b.1.i (1993 version -- you can look up the latest
yourself):

"The DC resistance between tip and ring conductors, and between each of
the tip and ring conductors and earth ground, shall be greater than 5
megohms for all DC voltages up to and including 100 volts."

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html


Which is more in agreement with the less than 10uA *ON*hook current that I
recalled seeing in my errant youth when phone phreaking...

"Oppie" wrote in message
...

Which is more in agreement with the less than 10uA *ON*hook current that I
recalled seeing in my errant youth when phone phreaking...

Which reminds me - check any of the alt.2600 usenet groups (lairs of the
phone phreaks)

"Oppie" wrote in message
...

Which is more in agreement with the less than 10uA *ON*hook current that I
recalled seeing in my errant youth when phone phreaking...

Which reminds me - check any of the alt.2600 usenet groups (lairs of the
phone phreaks)

Jim Thompson wrote:

How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

Why not ask Ma Bell?

Good Luck!
Rich

Jim Thompson wrote:

How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?

Why not ask Ma Bell?

Good Luck!
Rich

"BobW" wrote in message
...
We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he did
similarly creative/ugly things when generating (NTSC) color on the Apple II,
adding almost no cost to the design in the process. Such a feat was largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.

---Joel

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he did
similarly creative/ugly things when generating (NTSC) color on the Apple II,
adding almost no cost to the design in the process. Such a feat was largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he did
similarly creative/ugly things when generating (NTSC) color on the Apple II,
adding almost no cost to the design in the process. Such a feat was largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

flipper:

Not much *ON* hook since 20mA would trigger off hook detection, and
that's the 'guaranteed' value. It's less in reality. Up to about 4mA
would probably be ok.

If you are connected to a private PABX, not to a central office.

Here in Italy the maximum resistance tolerated is about 4 M.
Lower resistances will trigger an investigation on circuit losses.

F. Bertolazzi:

Here in Italy the maximum resistance tolerated is about 4 M.

Minimum, clearly.

In the US should be 5 Megaohms.

"BobW" wrote in message
...

"Oppie" wrote in message
...
[snip]
Which is more in agreement with the less than 10uA *ON*hook current that
I recalled seeing in my errant youth when phone phreaking...

"Errant", maybe, but it sure was a lot of fun.


I still look back with a smile on how the public utilities were mandated to
have technical documents on file in certain libraries. I know that here in
New York, the Ma Bell stuff was on file at Cornell University and Clarkson
College (where I attended). Both campuses became active phone phreakery
sites. You'd think the bigwigs would have put the documents in a liberal
arts school rather than engineering schools...

At the point when the phone company moved to electronic switching systems,
tracking of theft of service went into high gear. Most of the 315 area code
(Northern NY) was configured to put a hold and trace on any circuit (outside
of legitimate ones) where a 2600Hz tone was detected.
In an interesting twist of fate, my daughter re-married and her
father-in-law is a retired phone company investigator who was involved
big-time in hunting down phone phreaks. Nice guy, very smart and I'm very
happy that I never had a chance to meet him in his official capacity...

Oppie

"Jim Thompson" wrote in
message ...
How much current can you draw from a phone line (on-hook condition)
without annoying Ma Bell?


Strip out a few old speakerphones - the one's that don't have a battery
compartment often have a high voltage-very low current inverter to maintain
the supercap at a much lower voltage.

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the
tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he
did
similarly creative/ugly things when generating (NTSC) color on the Apple
II,
adding almost no cost to the design in the process. Such a feat was
largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.


AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

"Michael A. Terrell" wrote in message
...
Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty.

No, but from Woz's description of how it worked, I'm not surprised. Even he
says he wasn't sure it would really work on all TVs!

But for a hack that didn't cost much of anything, it's still quite clever.

The first computers I used were Apple II's and Commodore PETs (before the C-64
came out), and honestly... I'm amazed Commodore survived its PET era to go on
to make the (very good) C-64 -- compared to the Apple II, the original PETs
were quite crude. (...and the story goes that this was even after Chuck
Peddle had talked directly to Woz and knew a lot of how the Apple II was being
designed. Although, on the other hand, Peddle deserves a lot of credit for
realizing that a cheap CPU would completely revolutionize the industry...)

I find the entire history of the 8-bit computer industry quite fascinating --
it really demonstrated how a few smart guys (most of them without college
degrees) created widgets that were years ahead of what much-better-funded
large companies such as HP, IBM, Wang, and so on could cook up.

The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

They did it "properly" (in the VIC-II) chip by taking their 14.318MHz crystal
oscillator, generating quadrature signals at 3.58MHz, and then adding in
various ratios of I and Q to get the desired phase shifts. Their hue (I/Q or
U/V), then, ended up as the ratio of a couple of on-chip resistors -- quite
decent -- but their intensity was a function of an on-chip resistor's raw
value -- kinda crappy. The story goes that Commodore was too cheap to let
them add, e.g., an external 1% resistor so that intensity could be reasonably
accurate as well:
http://unusedino.de/ec64/technical/m...ors/index.html

---Joel

"BobW" wrote in message
...
Great story. Did you ever discuss your escapades with your daughter's
father-in-law? I would have loved to have seen his face.

We started goofing around after the famous Esquire magazine article was
published with its interview with Capt. Crunch. We didn't have access to
any official docs, but the book "Basic Telephone Switching Systems" was
all we needed to build the blue boxes. I still have a copy of it.

Besides blue boxes, I built this thing labeled a "black box". It worked
with incoming calls and would simply create a momentary offhook condition
and then cap couple the phone to the line. Its effect was that the calling
party would not get billed, but the two ends could talk. I'm not sure why
it worked because there was no loop current to power the carbon mic.

Bob

Yep, spent many an hour at family get-togethers talking with 'Pops' about
his career in the phone company and my involvement in the darker side of
such. What the heck, statute of limitations is long past.

Black box iirc was simply a zener diode in series with the phone line. Only
worked for incoming calls. We put the zener on a bridge rectifier so
polarity was not important. Seem to recall about a 40V zener. Idea was to
keep the line voltage high so that the CO would think that phone was still
on-hook. Low audio but was worth it for speaking long distance to the
girlfriend.
Audio will pass while ringing (unless this has changed). Not sure if the CO
detects line current or voltage for Off-hook. Would guess Voltage since the
zener trick worked.

Been a while since I checked out the news:alt.2600 and similar groups.
Oppie

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the
tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he
did
similarly creative/ugly things when generating (NTSC) color on the Apple
II,
adding almost no cost to the design in the process. Such a feat was
largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

Joel Koltner wrote:

"Michael A. Terrell" wrote in message
...
Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty.

No, but from Woz's description of how it worked, I'm not surprised. Even he
says he wasn't sure it would really work on all TVs!

But for a hack that didn't cost much of anything, it's still quite clever.

The first computers I used were Apple II's and Commodore PETs (before the C-64
came out), and honestly... I'm amazed Commodore survived its PET era to go on
to make the (very good) C-64 -- compared to the Apple II, the original PETs
were quite crude. (...and the story goes that this was even after Chuck
Peddle had talked directly to Woz and knew a lot of how the Apple II was being
designed. Although, on the other hand, Peddle deserves a lot of credit for
realizing that a cheap CPU would completely revolutionize the industry...)

I find the entire history of the 8-bit computer industry quite fascinating --
it really demonstrated how a few smart guys (most of them without college
degrees) created widgets that were years ahead of what much-better-funded
large companies such as HP, IBM, Wang, and so on could cook up.

The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

They did it "properly" (in the VIC-II) chip by taking their 14.318MHz crystal
oscillator, generating quadrature signals at 3.58MHz, and then adding in
various ratios of I and Q to get the desired phase shifts. Their hue (I/Q or
U/V), then, ended up as the ratio of a couple of on-chip resistors -- quite
decent -- but their intensity was a function of an on-chip resistor's raw
value -- kinda crappy. The story goes that Commodore was too cheap to let
them add, e.g., an external 1% resistor so that intensity could be reasonably
accurate as well:
http://unusedino.de/ec64/technical/m...ors/index.html


I had $65,000 worth of Metrodata character generators at a CATV head
end (2 systems * 4 channels each). They used 6845 Video chips and a 6800
CPU per system on the Motorola Exorcisor bus. There was 48 KB of RAM per
system. The C-64 was better quality, and a whole lot cleaner than the
Apple II used on our community loop by the local school system. Even
with it's 12 line, 22 column display you could barely read it.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

On Tue, 01 Mar 2011 22:05:55 -0500, "Michael A. Terrell"
wrote:


Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he did
similarly creative/ugly things when generating (NTSC) color on the Apple II,
adding almost no cost to the design in the process. Such a feat was largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

But, the C64 had a really bad vertical sync pulse that created a lot
of problems for various monitors. It sorta looked like an inverted
ramp, with a sharp front edge that then had an exponential curve up to
the front porch. I had a sync stretcher that got it to work for my
system...

Charlie

flipper:

I guess your regs don't allow line powered phones with caller ID and
phonebook dialers

They do, provided the telephone has a separate power supply.
Probably also a supercap, charged while off-hook, would do the trick.

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all
the
tones
digitally.

He became quite good at abusing digital chips for analog purposes --
he
did
similarly creative/ugly things when generating (NTSC) color on the
Apple
II,
adding almost no cost to the design in the process. Such a feat was
largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually,
as
volumes increased and prices dropped -- outperformed Woz's approach on
a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz

That would probably be a simple divide by 4, the PAL system effectively
requires 2 subcarrier bursts in quadrature, using a 4x crystal and a
quadrature divider neatly avoids the conventional (semi) analogue approach
of shifting the subcarrier oscillator in a PLL.

I remember the loss-leader Jap TVs that wiped out our industry. Some makes
had 2 subcarrier crystals, one synchronised to the primary subcarrier and
the other to the quadrature phase.

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all
the
tones
digitally.

He became quite good at abusing digital chips for analog purposes --
he
did
similarly creative/ugly things when generating (NTSC) color on the
Apple
II,
adding almost no cost to the design in the process. Such a feat was
largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually,
as
volumes increased and prices dropped -- outperformed Woz's approach on
a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz

That would probably be a simple divide by 4, the PAL system effectively
requires 2 subcarrier bursts in quadrature, using a 4x crystal and a
quadrature divider neatly avoids the conventional (semi) analogue approach
of shifting the subcarrier oscillator in a PLL.

I remember the loss-leader Jap TVs that wiped out our industry. Some makes
had 2 subcarrier crystals, one synchronised to the primary subcarrier and
the other to the quadrature phase.

"Charlie E." wrote:

On Tue, 01 Mar 2011 22:05:55 -0500, "Michael A. Terrell"
wrote:


Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he did
similarly creative/ugly things when generating (NTSC) color on the Apple II,
adding almost no cost to the design in the process. Such a feat was largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

But, the C64 had a really bad vertical sync pulse that created a lot
of problems for various monitors. It sorta looked like an inverted
ramp, with a sharp front edge that then had an exponential curve up to
the front porch. I had a sync stretcher that got it to work for my
system...


I fed one (SX-64) into a early '50s vintage 25 KW UHF TV transmitter
for a video test generator and it looked good on the output of the
demodulator. If you had one of the very early units with the white
ceramic Video chips with a gold cap, I've heard of problems with those,
but they looked like crap anyway. There were several revisions of the
video chip over the years.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

"Charlie E." wrote:

On Tue, 01 Mar 2011 22:05:55 -0500, "Michael A. Terrell"
wrote:


Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all the tones
digitally.

He became quite good at abusing digital chips for analog purposes -- he did
similarly creative/ugly things when generating (NTSC) color on the Apple II,
adding almost no cost to the design in the process. Such a feat was largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually, as
volumes increased and prices dropped -- outperformed Woz's approach on a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

But, the C64 had a really bad vertical sync pulse that created a lot
of problems for various monitors. It sorta looked like an inverted
ramp, with a sharp front edge that then had an exponential curve up to
the front porch. I had a sync stretcher that got it to work for my
system...


I fed one (SX-64) into a early '50s vintage 25 KW UHF TV transmitter
for a video test generator and it looked good on the output of the
demodulator. If you had one of the very early units with the white
ceramic Video chips with a gold cap, I've heard of problems with those,
but they looked like crap anyway. There were several revisions of the
video chip over the years.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

Ian Field wrote:

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all
the
tones
digitally.

He became quite good at abusing digital chips for analog purposes --
he
did
similarly creative/ugly things when generating (NTSC) color on the
Apple
II,
adding almost no cost to the design in the process. Such a feat was
largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually,
as
volumes increased and prices dropped -- outperformed Woz's approach on
a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz

That would probably be a simple divide by 4, the PAL system effectively
requires 2 subcarrier bursts in quadrature, using a 4x crystal and a
quadrature divider neatly avoids the conventional (semi) analogue approach
of shifting the subcarrier oscillator in a PLL.

I remember the loss-leader Jap TVs that wiped out our industry. Some makes
had 2 subcarrier crystals, one synchronised to the primary subcarrier and
the other to the quadrature phase.


And you try to tell me PAL was better! ;-)


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

Ian Field wrote:

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all
the
tones
digitally.

He became quite good at abusing digital chips for analog purposes --
he
did
similarly creative/ugly things when generating (NTSC) color on the
Apple
II,
adding almost no cost to the design in the process. Such a feat was
largely
unmatched for years; it was really only complete graphics ICs like the
Commodore VIC and perhaps the Motorola 6845/6847 that -- eventually,
as
volumes increased and prices dropped -- outperformed Woz's approach on
a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor? The
ones I saw were nasty. The C64 was cleaner than some low end ($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz

That would probably be a simple divide by 4, the PAL system effectively
requires 2 subcarrier bursts in quadrature, using a 4x crystal and a
quadrature divider neatly avoids the conventional (semi) analogue approach
of shifting the subcarrier oscillator in a PLL.

I remember the loss-leader Jap TVs that wiped out our industry. Some makes
had 2 subcarrier crystals, one synchronised to the primary subcarrier and
the other to the quadrature phase.


And you try to tell me PAL was better! ;-)


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

Well before the Blue Box era, friends had phun with pay phones.

All the upper housing were keyed alike so a repairman needed but
one key. The lock of a 3-gonger was a proud Bell System
invention, the 10G. So they patented it. And the key.
[Or was just the key labeled "10G"; don't recall.]

And that Bell System-wide key was cut *just as shown in the
patent filing..*

So they made their own keys. And when Ma had the audacity to
raise the price to TEN CENTS; they went around and lowered them
to a nickel again...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote in message
...

Well before the Blue Box era, friends had phun with pay phones.

Nice!

We used to take a wrapper from a stick of juicy Fruit gum, the foil over
paper one, put a slight curl on it so it would slide between the base and
pay phone. This worked on the older style (1960's era) pay phones. You would
slide the foil in on the right side at about the middle then slide it slowly
up and down till it shorted out the magic connections. Voila, a dial tone
and you could make a local call.

I heard reports of the 'impenetrable pay phone' (early 70's) being deployed
at Cornell University. Supposedly the phone had been removed from the wall
by the 'inquisitive' folks, reverse engineered and hacks distributed within
a day of deployment...

On 3/4/2011 10:44 AM, Oppie wrote:
"David Lesher" wrote in message
...

Well before the Blue Box era, friends had phun with pay phones.

Nice!

We used to take a wrapper from a stick of juicy Fruit gum, the foil over
paper one, put a slight curl on it so it would slide between the base
and pay phone. This worked on the older style (1960's era) pay phones.
You would slide the foil in on the right side at about the middle then
slide it slowly up and down till it shorted out the magic connections.
Voila, a dial tone and you could make a local call.

I heard reports of the 'impenetrable pay phone' (early 70's) being
deployed at Cornell University. Supposedly the phone had been removed
from the wall by the 'inquisitive' folks, reverse engineered and hacks
distributed within a day of deployment...

Pay phones in some locations used three wires, the third wire was
ground. The ground was used to activate the transfer of the coins from
the holding location to either the money box (for a completed call) or
the coin return (for a failed call). Open the ground and the money
stayed in the holding location. Make your call (long distance even) with
the ground open. Pay, then hang up. A few seconds later, reconnect the
ground and make a call to a number which you knew was either busy
(usually the number of the phone you were at!) or would not be answered.
Then hang up and the coins from both calls would drop into the coin return.

It got so the operators would listen for the 'crash' of the coins going
into the coin box, and if that didn't happen, they'd ask the user if
they heard it! Of course the user always said yes. Later users got smart
and had a box that they dropped coins in at the right time, to make the
appropriate sound.



--
I'm never going to grow up.

David Lesher wrote:

Well before the Blue Box era, friends had phun with pay phones.

All the upper housing were keyed alike so a repairman needed but
one key. The lock of a 3-gonger was a proud Bell System
invention, the 10G. So they patented it. And the key.
[Or was just the key labeled "10G"; don't recall.]

And that Bell System-wide key was cut *just as shown in the
patent filing..*

So they made their own keys. And when Ma had the audacity to
raise the price to TEN CENTS; they went around and lowered them
to a nickel again...

I once made a long-distance call with slugs.

Cheers!
Rich

flipper:

On Thu, 3 Mar 2011 12:32:15 +0100, "F. Bertolazzi"
wrote:

flipper:

I guess your regs don't allow line powered phones with caller ID and
phonebook dialers

They do, provided the telephone has a separate power supply.

Separate power supply isn't line powered.

Gosh.

Possibly. I haven't looked at the schematics of one but it seems a bit
iffy to me that the phone would quit working if you haven't made a
recent call.

The caller-ID enabled phones distributed by Telecom Italy have two AA
batteries.

I should note I wasn't saying he could get it FCC certified. I was
just suggesting he might get away with it.

Right.

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all
the
tones
digitally.

He became quite good at abusing digital chips for analog
purposes --
he
did
similarly creative/ugly things when generating (NTSC) color on the
Apple
II,
adding almost no cost to the design in the process. Such a feat
was
largely
unmatched for years; it was really only complete graphics ICs like
the
Commodore VIC and perhaps the Motorola 6845/6847 that --
eventually,
as
volumes increased and prices dropped -- outperformed Woz's approach
on
a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor?
The
ones I saw were nasty. The C64 was cleaner than some low end
($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz

That would probably be a simple divide by 4, the PAL system effectively
requires 2 subcarrier bursts in quadrature, using a 4x crystal and a
quadrature divider neatly avoids the conventional (semi) analogue
approach
of shifting the subcarrier oscillator in a PLL.

I remember the loss-leader Jap TVs that wiped out our industry. Some
makes
had 2 subcarrier crystals, one synchronised to the primary subcarrier and
the other to the quadrature phase.


And you try to tell me PAL was better! ;-)


Better than Never Twice the Same Colour anyway.

Ian Field wrote:

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
m...

Ian Field wrote:

"Michael A. Terrell" wrote in message
...

Joel Koltner wrote:

"BobW" ? wrote in message
...
? We sure had fun - as did Jobs and Wozniak (from what I read).

One of Wozniak's claims to fame was that his blue box generated all
the
tones
digitally.

He became quite good at abusing digital chips for analog
purposes --
he
did
similarly creative/ugly things when generating (NTSC) color on the
Apple
II,
adding almost no cost to the design in the process. Such a feat
was
largely
unmatched for years; it was really only complete graphics ICs like
the
Commodore VIC and perhaps the Motorola 6845/6847 that --
eventually,
as
volumes increased and prices dropped -- outperformed Woz's approach
on
a
price/performance basis.


Did you ever look at that Apple II video on a waveform monitor?
The
ones I saw were nasty. The C64 was cleaner than some low end
($1000)
NTSC Color character generators.

AFAICR the PAL standard Commodores used a 4x 4.433MHz crystal with a
quadrature divider to avoid a lot of complicated analogue stuff.

I never saw a PAL version, but the NTSC was 4*3.57954545 MHz

That would probably be a simple divide by 4, the PAL system effectively
requires 2 subcarrier bursts in quadrature, using a 4x crystal and a
quadrature divider neatly avoids the conventional (semi) analogue
approach
of shifting the subcarrier oscillator in a PLL.

I remember the loss-leader Jap TVs that wiped out our industry. Some
makes
had 2 subcarrier crystals, one synchronised to the primary subcarrier and
the other to the quadrature phase.


And you try to tell me PAL was better! ;-)

Better than Never Twice the Same Colour anyway.


Sigh. Are you living 30+ years in the past?


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.