I bought a house a while back, and it had a traditional home alarm system.  It was originally Broadview, which is ADT now.

I have stickers and signs:


I have a keypad like this, and a few keyless entry fobs:


I also have this Honeywell circuit board in the basement under the floor joists:


I'm not sure what all bells and whistles it has.  But whenever you open or close an exterior door, it beeps throughout the house (which is nice), it has an alarm, had monitoring, has at least one motion detector (although I can't find it), etc.  

What the home-seller didn't tell us was the passcode for the alarm.

After living in the house for about a week, my girlfriend arms it.  At that point, we did not know how to disarm it.  We found out that the alarm is pretty loud during the three times it went off, and what rooms we were 'trapped' in because of the motion detector.  Calls to the seller's real estate agent (who called the seller) were useless, they refused to give us the alarm code.  

After several calls to customer service, I eventually found the backup battery hidden in one closet, and then disconnected the powersupply in the basement, and everyone is quiet.  Except I have an old-fashioned, wired alarm system that I'm not using.

Now I want to get back into having a home security system. ADT says I would have to buy some new equipment, plus there is the costly monthly monitoring, etc.  
I've read some threads about SImpliSafe.  Is there a way to use what I already have, maybe change out the proprietary Broadview/Brinks/ADT parts, and get a local monitoring company?  I am pretty sure I will have to get some new parts because I do not know the passcode to this one and once I plug it back up, it will start alarming again  Or should I just forget about using it, and go with Simplisafe?  

OP, any alarm company that installs or works on that brand alarm can re-program your system.  It's not a bad idea anyway.  If your alarm isn't monitored, it should be.  Otherwise it's just a noise maker that your neighbors will probably ignore.  Hard wired is usually more reliable than wireless.

 
The latest generation of wireless sensors is suppose to be pretty reliable. Fully monitored so there is no worry about dead batteries or out-of-range issues. Or at least that is what I learned while researching Honeywell systems.

Did you have a legacy system when you were making your decision?  After your research, where did you land?  What system did you choose?  

I'm in the same boat as the OP:  just bought a house w/ an ADT system that had been turned off by the owner [who died] and his estate doesn't know anything/any codes ...

I am wondering if there is some way to use the wiring, go wireless, reprogram for local monitoring.  ADT wants $42/month monitoring, and it was an ADT franchise who put it in so isn't interested in reprogramming it    They don't seem to understand the concept of incremental revenue to meet competitors.  Anyroad,

So, like the OP, my questions are identical and looking into the hives thoughts: should I start from scratch, re-use the wiring, re-use parts of the sytem, revive the system [somehow]?  

Thanks,

 
I had a Simplisafe system and switched to a Honeywell Vista panel and wireless sensors. I have a thread in this subforum covering my install. IIRC, ADT also uses Honeywell panels and they cannot be reprogrammed in most cases. But just the board is pretty cheap assuming the rest of the sensors are compatible. Then you can get monitoring for as little as $10/mo from various places.

Find a local alarm company, ask them what their monthly rate is, & how much to replace the panel/keypad.

ADT is one of the ridiculously priced companies that only cares that they lock you into a contract; they have no actual incentive to make you happy.
You can probably find a company to do it for $17-20 per month, maybe even less.

If you can find a company that is familiar with Ademco/Honeywell systems he can probably bump the panel & unlock it.
Or have a local company give you a new panel & keypad too.

I have an envisalink module on my Vista20p panel and self monitor. It sends me text messages about activity, which I can then log into my cameras to check out.

The other day the internet went down while I was out, I got the text saying my panel lost communication. I get home and restarted the modem and it shoots me a text telling me the network has been restored.

It can send you texts about everything, including when the panel is armed and disarmed.

The Vista20p basically lets you do two separate alarms. Meaning some of my sensors are setup so they are grouped together as zone 2 so I can keep them armed at all times, because my wife doesn't arm the main when she leaves, but my gun safe area is always armed.

Not that I'm a home security system expert or anything, but I'm a fan of the Honeywell stuff.  A Vista 20P panel is a great basis for most systems and there is a ton of flexibility via the available sensors and modules.  DIY is more involved than something like Simplisafe.  I use a combination of wired and wireless sensors and use relay modules to control garage doors, etc.  If running wire to a particular door, window, or asset is difficult I don't really have any reservations about using the wireless sensors other than the up front cost.  That's the price you pay for convenience though.

ETA:  If there is existing wiring (and wired sensors) in a home, you can reuse it with a different panel in most cases.

Don't let ADT install any alarm equipment with an agreement to start a contract. If and when you're finished with their monthly monitoring and paying the higher than average monthly fee, they'll disable you're alarm and you won't be able to use it as a stand-alone system!  This is even well beyond the contract time limit (ask me how I know). Also, this is likely the reason some posters in this thread are describing alarm systems that are not usable.

Just buy a New panel and key pass off eBay that has been factory defaulted. Took about 10 min to swap the panel and the wiring and another hour or so to figure out the programming.  I went with dsc. But the invista listed above as anther good one.

Panel and two pads were around $50 shipped

Wires are wires. If you have wires use a hard wired device, where you need wireless to fill in a gap, it is easy. New panel, few new devices, but not a new contract. The hard part of running wires, power is done, make use of the stuff you have.