Bell 202 Modem (Demod Section), Implemented in Analog?

[Jim Thompson]

Anyone have a schematic of a Bell 202 Modem (only the demodulation
section needed), implemented in analog? (No DSP.)

Thanks!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[John Larkin]

On Sun, 28 Sep 2003 12:24:09 -0700, Jim Thompson
<invalid@invalid.invalid> wrote:

Anyone have a schematic of a Bell 202 Modem (only the demodulation
section needed), implemented in analog? (No DSP.)

Thanks!

...Jim Thompson

Well, the original 202 wasn't DSP! It had a lot of inductors as I
recall, as most of the old Bell stuff did.

This is simple 1200 baud FSK, 1200/2200 Hz carrier freqs. I've done it
two ways:

1. Fire a dual one-shot, one section on each edge, widths maybe 600
usec. Resistively sum the Q outputs into a 2 or 3-pole S-K lowpass
filter, then slice. Classic tach.

2. Exar makes an ancient PLL chip that will demod this. I have a
schematic at work somewhere, I think, if you're interested.

John

 

[George R. Gonzalez]

"Jim Thompson" <invalid@invalid.invalid> wrote in message
news:45denvc6biuqvdu7utcgeg0bpa5jc9n0se@4ax.com...

Anyone have a schematic of a Bell 202 Modem (only the demodulation
section needed), implemented in analog? (No DSP.)

Thanks!

Ah, good old FSK.

I've built many a ham-band modem out of a pair of tuned toroids and a
comparator,
either an IC or a bunch of ad-hoc cascaded transistors.

Or in later days, the venerable National 565 PLL, then later the CMOS 4046.

All the above can do an EXCELLENT job of pulling data out of weak very noisy
signals bounced to us
on the ionosphere from PAP: te Polish news service, or whatever. I recall
many a happy evening
watching the Reuters "Motorcycle with side-car" race results coming in on
the old
"1200-pieces of steel wiggling in formation", the Teletype Model 15.

Look at the ooold spec sheet for the National LM565, I think it had several
modem designs in there.
I've used that design with excellent first-time results.

Only problem is it needs a bit of offset tweaking to keep the comparator
biased slightly towards the "mark" channel.

 

[Gregg]

Heh, I see those for a dime a dozen at Value Village.

*starts singing "Memories"*

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

 

[George]

In article <45denvc6biuqvdu7utcgeg0bpa5jc9n0se@4ax.com>,
invalid@invalid.invalid says...

Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?
(No DSP.)

Going to be listening in on Caller ID, Jim?

In the olden days there was an Exar chip, the XR-2211, which
was specifically an FSK Demodulator - everything on one
14-pin chip, including a carrier detect output. I doubt the
chip is still available, but you might be able to run down
the data sheet to see how they did it.

 

[Watson A.Name - "Watt Sun]

In article <45denvc6biuqvdu7utcgeg0bpa5jc9n0se@4ax.com>,
invalid@invalid.invalid mentioned...

Anyone have a schematic of a Bell 202 Modem (only the demodulation
section needed), implemented in analog? (No DSP.)

Thanks!

Hey, I'll give you the whole modem! We still use one for the link
between the CO and our PBX, and I keep a couple spares, but I've never
had one fail. I still have the user manuals for 'em, probably from
the late '70s or early '80s; naturally they're all analog. All I know
is that when I pull the cover off, there are a ton of 1% resistors on
the board. Lots of filters, I'd say.

But rather than burden of reverse engineering one, I'd use an Exar
XR2206 or XR2211 chip, I forget which is the receiver.

...Jim Thompson

--
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[Jim Thompson]

On Sun, 28 Sep 2003 16:01:57 -0500, George <gh424NO845SPAM@cox.net>
wrote:

In article <45denvc6biuqvdu7utcgeg0bpa5jc9n0se@4ax.com>,
invalid@invalid.invalid says...

Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?
(No DSP.)

Going to be listening in on Caller ID, Jim?

In the olden days there was an Exar chip, the XR-2211, which
was specifically an FSK Demodulator - everything on one
14-pin chip, including a carrier detect output. I doubt the
chip is still available, but you might be able to run down
the data sheet to see how they did it.

Caller-ID... Yep! With the ring-killer circuit we discussed awhile
back I'm going to not even have a ring inside the house if I don't
recognize the caller-ID. General unrecognized CID will roll to
voice-mail; CID recognized as telemarketer will be picked-up then
hung-up all automatically (maybe even play a fax tone-set before
hang-up ;-)

I'm reluctant to use any ancient parts.

I'm trying to remember a scheme I used years ago that emulated the
"S-curve" of an FM discriminator using an All-Pass active filter.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[Winfield Hill]

Watson A.Name - "Watt Sun wrote...

Jim Thompson wrote:
Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?

But rather than burden of reverse engineering one, I'd
use an Exar ... XR2211 chip

Jim, I can send you .pdf files of the '2211 if you like.
Includes block diagrams, formulas and an IC schematic.

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Jim Thompson]

On 28 Sep 2003 14:28:52 -0700, Winfield Hill
<Winfield_member@newsguy.com> wrote:

Watson A.Name - "Watt Sun wrote...

Jim Thompson wrote:
Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?

But rather than burden of reverse engineering one, I'd
use an Exar ... XR2211 chip

Jim, I can send you .pdf files of the '2211 if you like.
Includes block diagrams, formulas and an IC schematic.

Thanks,
- Win

whill_at_picovolt-dot-com

Thanks, Win, I'd appreciate that.

Is the '2211 readily available?

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[Jim Thompson]

On Sun, 28 Sep 2003 12:24:09 -0700, Jim Thompson
<invalid@invalid.invalid> wrote:

Anyone have a schematic of a Bell 202 Modem (only the demodulation
section needed), implemented in analog? (No DSP.)

Thanks!

...Jim Thompson

Thanks to Win and Gregg for the data XR2211 sheets!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[Dave Turner]

Jim Thompson <invalid@invalid.invalid> wrote:

On 28 Sep 2003 14:28:52 -0700, Winfield Hill
Winfield_member@newsguy.com> wrote:

Watson A.Name - "Watt Sun wrote...

Jim Thompson wrote:
Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?

But rather than burden of reverse engineering one, I'd
use an Exar ... XR2211 chip

Jim, I can send you .pdf files of the '2211 if you like.
Includes block diagrams, formulas and an IC schematic.

Thanks,
- Win

whill_at_picovolt-dot-com

Thanks, Win, I'd appreciate that.

Is the '2211 readily available?

It seems to be.

Circuit Specialists and Jameco both list them.

CS charges more but you can drive over to Mesa, AZ and pick up one for $4.20
or get one from Jameco for $1.79 if you're not in a hurry.

See:
http://www.circuitspecialists.com/prod.itml/icOid/6977

and

http://www.jameco.com/cgi-bin/ncommerce3/ExecMacro/Jameco/searchResult.d2w/report?sort=BKW&search=xr2211

I have thought about making a CallerId/no ring box myself but it is too far down
the list.

Will you post your design?

Regards,

Dave

 

[Jim Thompson]

On Mon, 29 Sep 2003 00:08:19 -0700, Dave Turner
<dmturner@primenet.com> wrote:

[snip]

I have thought about making a CallerId/no ring box myself but it is too far down
the list.

Will you post your design?

Regards,

Dave

Probably. I'll only keep it to myself it there's a ruling that
telemarketer calls are "free speech"... then I plan to profit.
Otherwise we can use it to blank politicians and charities ;-)

I've already figured out the ring-blanking yet pass the CID onto the
house phones (in case you actually pick-up).

A lot of the project will be software, done by my oldest son, Aaron.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[George]

In article <rljenvk8l4anta133skn92mqp4knjbl5d5@4ax.com>,
invalid@invalid.invalid says...

Caller-ID... Yep! With the ring-killer circuit we
discussed awhile back I'm going to not even have a ring
inside the house if I don't recognize the caller-ID.
General unrecognized CID will roll to voice-mail; CID
recognized as telemarketer will be picked-up then
hung-up all automatically (maybe even play a fax
tone-set before hang-up ;-)

I built such a system several years back, but I used the
Motorola MC145447 Caller ID receiver chip, which not only
does the FSK demodulation and carrier detect, but also
removes the lead-in "U"s before the packet starts. And then
I used an old Commodore +4 computer for the brains of the
circuit. I probably have the only always-on Commodore +4 in
the entire world - up continually except for power outages
and upgrades since 1991.

I don't think Motorola makes that chip anymore.

I don't recall about the ring-killer discussion, but
remember that CID only comes in AFTER the first ring. In my
circuit I detect the beginning of the first ring with the
Moto chip, and then immediately open a relay that feeds all
of the phones with ringers turned on. So all I hear is a
little chirp. Then, if it's not a telescum, I close the
relay before the second ring starts.

And then I have it announce the caller audibly throughout
the house so I don't have to go look at the CID box.

But you know, for the demodulation part I would think you
would just use your voice modem. I think most of them have
Caller ID built in, and that would keep you from having to
build a demodulator at all.

 

[tk]

Jim

You might take a look here.... the AMS3144 is a rather simple solution to callerid
decoding.... they have been available here:

Ralph Landry
PO Box 1478
Lake Junaluska, NC 28745

Aptek AMS3144 Caller ID Hybrid
$7.00 each

My 10 year old smart telephone which does the things your planning. It uses a
Motorola chip 145xxxxx (obsolete) and a PIC 16C54 feeding an 8051 processor... I
can drop the Aptek callerid application note via USPS if you're interested.

Cheers

Ted in At;anta KD4EE...

Jim Thompson wrote:

On Mon, 29 Sep 2003 00:08:19 -0700, Dave Turner
dmturner@primenet.com> wrote:

[snip]
I have thought about making a CallerId/no ring box myself but it is too far down
the list.

Will you post your design?

Regards,

Dave

Probably. I'll only keep it to myself it there's a ruling that
telemarketer calls are "free speech"... then I plan to profit.
Otherwise we can use it to blank politicians and charities ;-)

I've already figured out the ring-blanking yet pass the CID onto the
house phones (in case you actually pick-up).

A lot of the project will be software, done by my oldest son, Aaron.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[Darcy Roberts]

Try the chips from Holtek HT9030 or similar.
Uses a single crystal, does all the right bits.

regards,
Darcy Roberts
(change the what to watt to reply)

Jim Thompson wrote:

On Sun, 28 Sep 2003 16:01:57 -0500, George <gh424NO845SPAM@cox.net
wrote:


In article <45denvc6biuqvdu7utcgeg0bpa5jc9n0se@4ax.com>,
invalid@invalid.invalid says...


Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?
(No DSP.)

Going to be listening in on Caller ID, Jim?

In the olden days there was an Exar chip, the XR-2211, which
was specifically an FSK Demodulator - everything on one
14-pin chip, including a carrier detect output. I doubt the
chip is still available, but you might be able to run down
the data sheet to see how they did it.




Caller-ID... Yep! With the ring-killer circuit we discussed awhile
back I'm going to not even have a ring inside the house if I don't
recognize the caller-ID. General unrecognized CID will roll to
voice-mail; CID recognized as telemarketer will be picked-up then
hung-up all automatically (maybe even play a fax tone-set before
hang-up ;-)

I'm reluctant to use any ancient parts.

I'm trying to remember a scheme I used years ago that emulated the
"S-curve" of an FM discriminator using an All-Pass active filter.

...Jim Thompson

 

[Gary Tait]

Whereas On Mon, 29 Sep 2003 20:31:25 -0400, Darcy Roberts
<darcy_roberts@htwhat.com> scribbled:
, I thus relpy:

Try the chips from Holtek HT9030 or similar.
Uses a single crystal, does all the right bits.

Such as http://www.npc.co.jp/en/product/ic/sm8223e.html

regards,
Darcy Roberts
(change the what to watt to reply)

Jim Thompson wrote:

On Sun, 28 Sep 2003 16:01:57 -0500, George <gh424NO845SPAM@cox.net
wrote:


In article <45denvc6biuqvdu7utcgeg0bpa5jc9n0se@4ax.com>,
invalid@invalid.invalid says...


Anyone have a schematic of a Bell 202 Modem (only the
demodulation section needed), implemented in analog?
(No DSP.)

Going to be listening in on Caller ID, Jim?

In the olden days there was an Exar chip, the XR-2211, which
was specifically an FSK Demodulator - everything on one
14-pin chip, including a carrier detect output. I doubt the
chip is still available, but you might be able to run down
the data sheet to see how they did it.




Caller-ID... Yep! With the ring-killer circuit we discussed awhile
back I'm going to not even have a ring inside the house if I don't
recognize the caller-ID. General unrecognized CID will roll to
voice-mail; CID recognized as telemarketer will be picked-up then
hung-up all automatically (maybe even play a fax tone-set before
hang-up ;-)

I'm reluctant to use any ancient parts.

I'm trying to remember a scheme I used years ago that emulated the
"S-curve" of an FM discriminator using an All-Pass active filter.

...Jim Thompson

--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

 

[kansas_ray]

"Jim Thompson" <invalid@invalid.invalid> wrote in message
news:h7hgnvcp3fs888etiel1e5b2u9ehm2bnd7@4ax.com...

A lot of the project will be software, done by my oldest son, Aaron.

...Jim Thompson

Hi Jim,

You said you want to avoid DSP but if "a lot of the project will be
software" then you should re-consider; especially if you plan to market it
later. Maybe both the *old* and *young* bull could learn something?

I won't waste your time with suggestions unless you're interested.

Best Regards,
Ray

 

[Jim Thompson]

On Wed, 01 Oct 2003 15:48:10 GMT, "kansas_ray"
<kansas_ray@hotmail.com> wrote:

"Jim Thompson" <invalid@invalid.invalid> wrote in message
news:h7hgnvcp3fs888etiel1e5b2u9ehm2bnd7@4ax.com...


A lot of the project will be software, done by my oldest son, Aaron.

...Jim Thompson

Hi Jim,

You said you want to avoid DSP but if "a lot of the project will be
software" then you should re-consider; especially if you plan to market it
later. Maybe both the *old* and *young* bull could learn something?

I won't waste your time with suggestions unless you're interested.

Best Regards,
Ray

"Software" for the PC, maintaining and comparing incoming CID with a
list... not exactly a DSP task.

The circuitry will simply convert CID tones to serial (or USB) format,
the PC will do the rest, issuing hang-up/answer commands as required.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[David Harmon]

On Sun, 28 Sep 2003 14:27:41 -0700 in sci.electronics.cad, Jim
Thompson <invalid@invalid.invalid> was alleged to have written:

CID recognized as telemarketer will be picked-up then
hung-up all automatically

Please make sure you wait at least two full seconds before hanging
up, to be sure they get charged for the call.

 

[Jim Thompson]

On Fri, 03 Oct 2003 08:42:58 GMT, David Harmon <source@netcom.com>
wrote:

On Sun, 28 Sep 2003 14:27:41 -0700 in sci.electronics.cad, Jim
Thompson <invalid@invalid.invalid> was alleged to have written:
CID recognized as telemarketer will be picked-up then
hung-up all automatically

Please make sure you wait at least two full seconds before hanging
up, to be sure they get charged for the call.

David, thanks for the tip, I'll build that feature in.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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