How did my alarm code change when I never touched it

How did my alarm code change when I never touched it?

(not a computer but it does have a digitally stored program, and solid state memory for the settings, less than 1000 bytes, I think.)

About 9 years ago I started to install a burglar alarm, but I didn't finish before I had to leave on my trip.

After I got home, I didn't care anymore.

I'm leaving on another trip soon and I started in on the alarm agailn.

Even thogh the trouble light is lit, It didn't need much to hook it up, but I couldn't arm it. Pressing the default arm code just let to a longer error-beep.

Eventually did a reset, what they call a Factory Default Main Panel.

Now the default arm code works.

I'm sure I never changed the code. My previous alarm worked for 15 years or more and I used the default code all that time, never considered chaning it**, and I was still trying to get the thing to work. Another reason not to change it.

So can things like this get messed up just be sitting around?. In my basement with cinder block walls. The only source of radiation is the

30 y.o. oil furnace. That coudln't do it. A small tv in the room too. There's a microwave upstairs.

**There are occasional burglaries around here, but none of these people know what the default alarm code is for anything. It's not like I live on the same street as the Vanderbilts or Morrgans.

BTW, it's funny. I wanted to see if the siren worked but the code didnt' work to arm the alarm. The third time I tried, I noticed the Away button. This contol panel doesn't require a code when leaving because they figure if you got in, you're trustworthy. So I armed it. Then I opened the door until the siren went off. Then I rmemebered I had no code to disarm it!!. I tried the code several times, again, but it didnt' work. I unplugged the thing, but when I plugged it in again, it armed itself. Of course. Otherwise, power failures when the battery is dead would disarm alarms. So I was trapped in the house. Eventually I disconnected the control panel from the siren driver, so it didn't make any noise the next time.

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Haven't a clue what is the hardware which you seem to deliberate omit in your posts. Could be the code gets stored in EEPROM but I doubt it since it would take sufficient voltage to reprogram the bits in the chip. Could be there is a capacitor on the PCB used to hold the code. That capacitor discharged long ago so any value stored in volatile memory is gone. Could be a battery is used instead of a capacitor. Just like your PC, a dead battery means the CMOS table's values (a copy of the BIOS and where you do your tweaks, like changing a login password) is corrupted or all values are unusable. That means the BIOS copy of the settings get loaded into the CMOS table.

If it uses EEPROM, something is wrong with the hardware that had it lose your stored code. If it uses a capacitor, well, those things only stay charged for a limited time. If it uses a battery, replace it as it is probably too old and doesn't have enough capacity (might have enough voltage under a no-load test but cannot supply any current, even a tiny bit, without a voltage drop).

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No, I didn't deliberately omit anything. I also didn't include it because I can't imagine anyone here knows details about any brand of alarm panel, who woudln't also know that they're mostly made the same.

It's a DSC Power 832. Does that actually help? There are things about it on the web, and I dl'd some manuals before I found my paper manuals, but I don't they give an answer.

But then how did resetting the panel get it back? Of course I could ask that question about any answer, I guess.

I don't think there's a battery. No mention in any manual and I didn't see one. Certainly no coin battery.

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"... the alarm panel has detected one or more ?trouble? conditions. These include things like battery trouble, ..." and "If your DSC home alarm is beeping due to this condition, the main panel battery is low or failing." and "If you?ve recently had a power outage, wait 24-48 hours after power is restored. The battery may simply have discharged, and will recharge when the electricity comes back on. If the beeping persists, the battery probably needs to be replaced."

There is a link to:

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So there is a battery. Looks like you are supposed to add one. The battery retains settings between power outages (but only however long the battery can provide power).

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Steve & Lynn

Oh, that battery. That's meant to power the panel and the siren and the dialer if there's a power failure. It's not meant to retain things in memory except user-decided things like the time and which zones are excluded. It's not meant to retain defaults. That's what makes them defaults. . When the board comes from the factory, it's not connected to the battery and it stays that way for weeks or months until someone sets up the whole system**, but the contol panel doesn't forget what the default alarm code is. **In fact, my friend who owns an alarm company (but who is not intereted in questions like the one in my OP) who is normally a stickler for things, agreed that I didnt' have to have a battery to run the alarm, since outages are so rare here.

I had looked on the DSC site but the manuals I found need needed permission to be downloaded. I have them in print but to use Find, it helps to have digital copies. Part of your url above is written specifically for DSC and it also linked to a place where I could dl the exact manual that I already have. Thanks a lot

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A few things:

Alarms from the factory have a DEFAULT code built in. It is not, or should not be the code you use on a daily basis, as if so, thousands of others hav e it. That code is USER DEFINED, after the initial code is entered. Maintai ning that user-defined code does require power. Think about why.

So, you need to determine from the manufacturer what the default code is fo r your make, model and assembly year - which will be from the serial number . In theory, that should give you the default code.

Keep in mind that the manufacturer should not balk at giving this to you as it was either printed or tagged on the device when new. Kinda-Sorta like b uying a safe. It comes with 12345 as the combination. Which you change (or not). But if you lose it, it is your problem. Electronics are a bit more fo rgiving in this sense.

Peter Wieck Melrose Park, PA

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That seems like an odd thing for your friend to say. Alarm systems have batteries so the bad guys can't disable them by cutting power to your house. Same with the phone lines used to dial out for help. It is easy to cut land lines. That's why newer alarm panels often use cellular. Not perfect, but it takes more knowledge and equipment to jam a cellular call than to cut landline phone wires.

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You cannot program anything without power - unless this panel has dip, toggle, or other types of switches to hardwire in that "data".

Another possibility (already mentioned) is the use of EEPROM; however, there would need to exist power to raise the voltage to burn in the new values. Are there EEPROMs on the PCB?

How can you enter and save a security code without there being power? Electronically it is possible when there exists power that will be saved after power is lost (battery, capacitor, EEPROM) - but you still need power during that operation. From the images I found online, there are no switches on the PCB for that device, just a 4-pin header (S1) where you use jumpers:

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Ah, finally found something:

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EEPROM memory - will not lose programming or system status on complete AC and battery failure I couldn't tell from the photos I found online if there was an EEPROM, plus the pics showed the component side of the PCB so I couldn't tell what, if anything, was on the other side. I cannot guarantee the above URL specifies only the 832 since the 5010 replaced it (and they might be showing the specs for the 5010).

An EEPROM still requires power to program it. EEPROM = electrically erasable programmable read-only memory. You need power to erase or program values into its storage. Some EEPROMs have a built-in charge pump to attain the higher voltage while others require external circuitry to apply the higher voltage. But the EEPROM requires power to program it. You said you entered in a new access code. That meant you must have connected it to power.

The values should stay in the EEPROM unless you did something by accident, like after plugging in the A/C power adapter. EEPROMs have a limited number of write cycles but I doubt you have programmed it a million times.

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(another possibility is a bad, weak, or leaky EEPROM)

There is mention of a maximum retention time of 10 years for values stored in EEPROMs. How long has this one been sitting idle and unconnected from power? *Oh oh*, "About 9 years ago I started to install a burglar alarm". I missed than in reading your original post. So you waited too long to refresh the EEPROM and the pics of the PCB don't exude an impression that this one has auto-refresh circuitry but then that would require power, too, and refreshing means more writes (so the EEPROM could get consumed by frequent refreshing).

The AlarmsBC web site has links to free manuals at:

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I clicked on "DSC" and found 2 manuals for the 832 (5010) depending on the version of the unit. I looked at version 1 of the manual. Page 7 says how to program the access codes. No mention of enabling a switch or jumpering of the S1 header to program the EEPROM. However, there must be power available when using the device, even to program the access codes. There is no troubleshooting section in their manual.

Looks like the *oh oh* problem is that you expected the EEPROM without refresh to retain its values forever. EEPROMs leak the charges (hopefully slowly) but those charges do dissipate over time. 9 years is too close to the 10-year claim for retention (and who knows what quality of EEPROMs went into this device).

[E]EPROMs have a shelf life regarding retention. They have a finite data retention time. DSC probably didn't expect something laying around for a decade to still need to use the same access code. Who'd remember that after a decade's absence? They begin to forget their data after 10-15 years. Yours was on the shy side of that. Mask ROMs don't have that problem because the values are etched (burned) permanently into the chip at production time. There are SuperFlash EEPROMs that claim data retention for 20-100 years (but that's still finite); see
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That was introduced back in 1993. Don't know if DSC used any. PC mobos adopted them.

After 10 years of absence (no refresh) with or without power is too long to expect no degradation (data corruption or loss) for EEPROMs.

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Thanks for all the advice. It will be valuabe for many people.

He knows the kind of crimes that happen here, and he knows them by neighborhood too (a few years ago he had 800 or maybe it was 1200 customers) , and where I live they don't use fancy tricks like cutting the power or phone lines. Did I mention I don't live near the Vanderbilts, or even any doctors or lawyers. (there also aren't many burglaries because a lot of burglars know there is more money in other n'hoods** )

Where I live they break in. If an alarm goes off, they grab what they can quickly and they leave quickly.

We did discuss routing the phone line, whether the alarm needed to interrupt the phone line to the phones (because that would be difficult to arrange here. The phone line no longer goes to the basement. I just use a cordless phone in the basement, where the alarm is, so the alarm telephone line and the telephone telephone-line are wired in parallel.). He pointed out three reasons why it should.

If the alarm is between the phones and the phone company, were I on the phone when the alarm went off, the call would be interrupted, and that would indicate (though not 100%) that the alarm had gone off. But I would also hear the siren , whether I'm on the phone or not. He knows that but he was being complete. (Plus I don't set the alarm when I'm home. Maybe if I get old and feeble I will.)

If he wants to do remote maintenance to the alarm, it works better, but he pointed out, all I would have to do is turn off my phone answering machine and not answer the phone.

If the alarm does not disconnect the phones, when the burglar comes in he can take a phone off the hook and stop the alarm from dialing out. (Is that true. i thought since touch tone, one phone could dial out even if another phone was off the hook. (I think I tested this once.) I thought the burglar would have to dial a number or two before the alarm finished, or started, dialing. That's not so hard because the phone doesn't dial absolutely immediately. It gives the owner a 10 or

20 seconds to put in the code for example. Maybe he meant all that but he simplified it for me.)

He sells those too.

** Not many burglaries. 9 years ago I went away for 8 weeks, couldn't get the alarm working in time, but the house was unchanged when I got back. And I've seen houses sit vacant for months without any damage at all. OTOH, kids broke into one vacant house and used it as a clubhouse until the police scared them out. And 34 years ago, the first summer, someone kicked open my front door though he didn't steal anything***, and another time two lawnmowers were stolen (both were very broken), and another a crummy bicycle without a seat or post was stolen. but the last two incidents didn't require going into the house. ***My burglar alarm was sitting on the bed or the floor, in pieces. I hadn't taken taken the parts out of the boxes yet. But I stayed home from work the next day and installed it.
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