duplicating phone and ring voltage

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I need to connect some telephone-type things together in my own little circuit, and test them, but I don't know a simple method or what voltages to use. I think I need to use some wire, some kind of DC power, something to put a ring-signal on the line, a phone, and whatever I am testing.
For example, I'm getting a replacement for my all-time favorite phone answering machine, but the owner has forgotten the 3-digit code for remote message retrieval. :( I'm willing to try all 900 or 1000, probably while I'm watching tv, but only if I can get it to go quickly. So I need a test line to ring it directly, have the machine answer, and punch in the code.
Also I have 2 fax machines, one that sends and one that receives! :) I'm pretty sure I can get it down to one that does both.
I don't have two phone lines, and even if I did, I think things would run quicker with my own little circuit.
In the 7th grade, we had two candlestick phones and a dry cell to play with during ham radio club, and everything worked (except it didn't ring, but that was ok because they had no bells. :) )
Any help appreciated.
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Phones need 48 Volts DC with an in series of 600 to 800 ohm source. The ring is 96 Volts at 25 Hz.
For the answering machine, if it is a name brand, you should be able to get the information about how to reset the remote code. If it is a fixed uninique code, then you have a problem. For what it is worth, maybe it would be better to simply get a new answering machine.
--

JANA
_____


"mm" < snipped-for-privacy@bigfoot.com> wrote in message
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snip

snip
Jana:
Seems like a lot of effort for short money (bad ROI)?
What Make and Model is this unit?
I bet we could find you one on e-Bay that doesn't entail hooking up multiple 12 volt batteries in series and punching in a possible 1,000 codes to get it to work!
Do you really want to sit amongst multiple car batteries in your living room watching TV punching in codes all night and then recharging them, trying 1,000 possible codes is going to take some time and will probably require one, or more, recharges.
Just my $.02 worth. Voicemail!!!!
Jay
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That's the spec to allow for vast voltage drop over the miles of cable between phones. Just to get two to talk to one another 9 volts will work just ok. Indeed if you're talking about old non electronics phones with carbon mics 1.5 volts will be ok for short runs.
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*Proofread carefully to see if you any words out or mispeld something *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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This is a multi-part message in MIME format. --------------010808020602090006000400 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit
Dave Plowman (News) wrote:

I have always used the assumptions that there was 400 Ohms in the telephone. The telephone wants 20 milli-Amps or more so that says you need 8 Volts or more (per phone) The 48 Volts (really 52) that the central office uses is to push at least 20 milli-Amps through the longest line.
Bill K7NOM
--------------010808020602090006000400 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> <title></title> </head> <body bgcolor="#ffffff" text="#000000"> Dave Plowman (News) wrote:
<pre wrap="">In article <a class="moz-txt-link-rfc2396E" href="mailto: snipped-for-privacy@uni-berlin.de">&lt; snipped-for-privacy@uni-berlin.de&gt;</a>, JANA <a class="moz-txt-link-rfc2396E" href="mailto: snipped-for-privacy@ca.inter.net">&lt; snipped-for-privacy@ca.inter.net&gt;</a> wrote: </pre> <blockquote type="cite"> <pre wrap="">Phones need 48 Volts DC with an in series of 600 to 800 ohm source. The ring is 96 Volts at 25 Hz. </pre> </blockquote> <pre wrap=""><!----> That's the spec to allow for vast voltage drop over the miles of cable between phones. Just to get two to talk to one another 9 volts will work just ok. Indeed if you're talking about old non electronics phones with carbon mics 1.5 volts will be ok for short runs.
</pre> </blockquote> I have always used the assumptions&nbsp; that there was 400 Ohms in the telephone. The telephone wants <br> 20 milli-Amps or more so that says you need 8 Volts or more (per phone) The 48 Volts (really 52)<br> that the central office uses is to push at least 20 milli-Amps through the longest line.<br> <br> Bill K7NOM<br> </body> </html>
--------------010808020602090006000400--
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Thanks a lot.

It is a fixed code. A friend of mine and I each bought one 21 years ago, and the code was printed on the box, not on the bottom of the unit that became more common. I wish it had been on the bottom; we would still have it! This new one is from the wife of a friend, and she stopped using it a couple years ago and has forgotten the code. :(
It's Code-a-Phone, model 2530 or similar model.

Like I say, this is my all-time favorite phone machine. I have about 10 others, all different brands or models, that I've bought in the last 2 or 3 years, paying 1 to 3 dollars each at hamfests. They all work as designed but I don't like how they work.
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wrote:

Found this in google for a Code-a-Phone model 2600.
"Not sure of the model number, but it sounds familiar. If it is the little black one with gold trim and the digital outgoing message, then the remote code is determinded by two things; a sticker on the bottom with a single digit (ie '7') and a switch with two numbers. ('3' or '9') The sticker determines the first digit, the switch selects the second digit. This may be true for yours, look on the bottom for a sticker with a single number; then look for the switch, it may be hidden."
<http://groups.google.ca/group/sci.electronics.repair/browse_frm/thread/53a6aaf7777ac05b/86ce2349e56f35b4?lnk=st&q=answering+machine+remote+control+code&rnum=4&hl=en#86ce2349e56f35b4
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On Fri, 31 Mar 2006 01:48:56 -0500, snipped-for-privacy@to.group wrote:

Thanks a lot, this could be very helpful. I don't have the machine in front of me right now, but I will look for these things.

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finger to keyboard and composed:

So you have another identical unit? Is it an analogue type, ie does it use microcassettes rather than flash memory? If so, then there may be a small 8-pin serial EEPROM that stores the code and speed dial numbers (?), in which case you could swap the chip between the two machines. You could also read the chips using a device programmer and compare the contents, or you could simply duplicate a working chip.
- Franc Zabkar
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Please remove one \'i\' from my address when replying by email.

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On Sat, 01 Apr 2006 07:48:32 +1000, Franc Zabkar

Microcassettes.
Not important, but it doesn't have a phone attached. That is one of the reasons my friend doesn't use it anymore.
I will look for the EEPROM.

*simply* duplicate? I don't think I can do that. ;-) But the rest of it sounds possible. Thanks a lot.

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Are you sure you can't just program a new access code without knowing the old one? My machine does not ask for any codes at the base unit for anything. The new code just replaces the old. Only remote access requires the code. But yours may be different.
Kevin
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there are little circuit boxes that immitate the phone line, last I saw one about 60 bucks
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Thats the way to go... Getting the operating voltage (48vdc) isn't that hard just hook up 4 12 volt batteries in series with an 800 ohm (If I remember correctly) reisistor on the end. Getting a 20hz ringtone is the difficult part since the wall current is 60hz.. I never figured out an easy way to make my phones ring.
- Mike
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There's several easy ways to generate a 25Hz at 96v, one is an old fashioned multivibrator driving a 120V/12V transformer secondary, (ie a 25Hz inverter) and adjusting the multivibrator's supply down to get 96V. It's rough and ready but there's no reason why it shouldn't work, and it uses a few standard, off the shelf components.
Dave
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Wish someone had told me that when I was trying to build a ring circuit.
Oh well I guess I know now. :-)
- Mike

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wrote:

Sounds good, but so far the cheapest one was 114 plus S&H. Maybe I'll find the model you saw.

I can handle this.

This sounds good, but I need to have it explained in simpler words. :(

Multivibrator?

25Hz inverter. All I can think of is the power supply from a tube radio in a 1950 car, that runs off a 6 (or 12) volt battery.

So I have to build it? I can do that but I don't know how. :)

Remove NOPSAM to email me. Please let me know if you have posted also.
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Here's a simple inverter-
http://www.repairfaq.org/REPAIR/F_samschem.html#SAMSCHEM_009
But to get more control over frequency you may need a more complex circuit using an astable multivibrator or timer IC like a 555.
Dave
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mm wrote:

Hmmm, In this digital age, playing with analog?
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Yup... It's called POTS Plain Old Telephone Service.
One thing to consider... Many fax machines and other devices have dial tone detection circuits. The mere presence of DC voltage on the line will not make them dial. Also, getting the correct 20 Hz ring frequency and voltage (with the right current) in a home grown circuit is a pain unless you are willing to get fairly elaborate.
Here is a fancy Ringdown Circuit from Viking Electronics. List price is $106
http://www.vikingelectronics.com/products/pdf/dle-200b (sm).pdf
Beachcomber
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Black magic ring generator-
http://www.camblab.com/home.htm
Dave
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