June 1998, Issue 95

Gotchya!
Alarming the Alarm System

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I was just about ready to pack it in for the night when Jeannette called down the cellar stairs.

"Steve, the alarm service is on the phone. The alarm at the office just went off! They called the police. Shall I say you’re on the way to meet them?"

As I grabbed my coat and keys, I cast a quick glance back at Jeannette. Her expression said far more than any verbal exchange.

The gist of it was that if anyone was going to play hero tonight, it wasn’t going to be her. She’s happy to run a business with me, but gunslinger is definitely not in her job description.

There was a time when sharing the "business experience" might have prevailed, but after a real break-in at our office when the police actually dragged a burglar out in handcuffs, she decided this was one event she’d rather stay away from. Besides, anyone stupid enough to break into a building attached to a courthouse and surrounded by a half-dozen TV cameras probably isn’t bright enough to listen to reason anyway.

As I ran for the car, I heard her yell, "Be careful…! Call me…!"

Like most businesses, we have a commercial alarm system. The reason isn’t as much to deter crime as it is to qualify for discount on insurance rates. That’s the good news.

The bad news is that, because I live closest to the office, I’m first on the call list when the alarm goes off. I get to greet the police and walk around a building with a lot of dark hiding places.

There really aren’t a lot of options. If you want the police to treat the call seriously, you better meet them there. And, you also have to watch the false alarms.

Everyone had a sense of humor when someone set the alarm while Ken was still working on the third floor. Since then, the last one out is supposed to page the building or check the parking lot. There has to be a bit of seriousness. After all, the police did nab somebody that one time.

As I pulled into the parking lot, the lights from state and local police cruisers greeted me. All I could think was, please, let them find Jeffery Dahmer or someone, not another false alarm.

After the appropriate introductions, we trooped into the building—they with their guns drawn and flashlights blazing. I don’t know why they didn’t just turn on the lights, but they preferred to search each room in the dark.

I still don’t understand the tactic. Maybe they presumed someone this dumb would invariably use tracer ammo or something else that’s easy to see in the dark. Needless to say, I waited until the lights were on before roaming anywhere unescorted.

The results of the search were less than spectacular and somewhat embarrassing. Apparently, workmen had left an outside door to the furnace room unlocked and nobody checked it.

Besides the lock, the door needs a 3½² thick wooden bar across the inside to keep it from opening. Of course, when someone leaves the door unlocked and only puts in a standard 2 ´ 4 (1¾" thick) instead of the usual 4 ´ 4, the door can open almost 2². Guess what happens when someone pulls on the door from outside? An unlocked door is an embarrassing predicament.

Needless to say, I apologized profusely. It was a false alarm. If we’d nabbed Charles Manson, wasting their time wouldn’t be an issue. I probably could have even gotten away making police and donut-shop jokes. Under the circumstances, however, my only recourse was to thank them, tuck my tail, and return to the car.

I dialed the cell phone. When Jeannette answered, I said in a disgusted tone, "Someone left the damn door open! The only thing worse would be if they didn’t set the alarm at all!"

"Well, Steve, I wasn’t going to tell you, but I’ve had reports from the people who come in early that occasionally the alarm hasn’t been on."

Next morning, I called everyone with alarm codes together and asked the pertinent who and when questions. I got back mostly blank stares, to be interpreted as, "Not me, man." Given all the people with independent access to the building, that was hardly reassuring.

The obvious answer was the alarm company. We pay them $30 a month to monitor the system and call the appropriate people if the alarm goes off. When it was first installed, we got a monthly opening/closing report that listed the date, time, and access code (these days I suppose we’d call it a PIN) for every alarm set or reset. This was the obvious answer.

Calling the alarm-monitoring service is an experience. They’re contracted by your alarm installer and not typically selected by the alarm owner. And since they answer the phone "Monitoring station" and use the installer’s name once you give them your account number, you might think they’re just down the block. Only when you interrogate the autodialer or otherwise see where the call goes do you realize that your personal monitoring can be 2000 miles away.

Our monitoring company was at the other end of the state, but most large alarm companies deal with centralized service monitors that cover many states at the same time. Regardless of their location, aside from changes to the call list, they’re like talking to a brick! Their pat response is that you should call your installer.

They usually charge the installer a flat rate based on a specific service level for all his customers. If he only contracts for alarm calling and none of the monthly printed reports, it’s tantamount to bringing the mountain to Mohammed to get one from the monitoring company. Yes, I could get a report for a specific day—at $20 each!

Calling the installer reminded me again why we designed our own home-control system. These people have no vision at all.

"What would it take to get daily entry/exit reports?" I asked.

"I suggest you install a new alarm system," he answered matter-of-factly.

"Would a new system be better than our present ten-year-old hard-wired system?"

"Well, sir," he continued. (Subconsciously, I noted that people generally called me "sir" when they were trying to sell me something. Sometime I’ll have to test the financial limits of this theory. Do they start at $100, $500, $1000…?) "It would have the latest technology and use wireless sensors."

"And after I replace the $2 battery in every sensor each year, would it do more than provide a contact closure to an alarm horn and autodial a digital code to the monitoring station like the present one?" I already knew the answer.

"It would use the latest technology to close the contact and autodial the modem, sir…and we could get you one with a printer output." Finally, he mentioned something we wanted!

I continued, "Do you know if it’s a standard serial printer port? Do you have a schematic?"

"Well, I’m not sure what it is, sir, but I can supply you with the printer (extra cost). There are never any schematics of any equipment, sir. I guess they’re concerned about liability."

Liability, schmiliability. The only reason there are no schematics is that the alarm manufacturers don’t want competition.

In the end, it’s just a cost decision. "How much?"

"Well, sir, if we do just the same as your present system and add the printer, probably about $3500–4000."

I knew this "sir" thing was going to cost me. "Thanks, I’ll have to get back to you."

My next stop was Jeff’s desk.

"Jeff, this alarm guy is nuts. You can’t believe how much it costs for an alarm-code printout. Worse yet, it only records successful entries. It can’t tell who punches in a bunch of numbers, never actually sets the alarm, and then just walks out without checking. That’s the guy I want."

I knew telling Jeff about such a ridiculous obstruction would be a technical challenge he couldn’t refuse. They may not know how to produce a daily event record, but somehow we would. We gathered up the ’scope and headed for the furnace room and the alarm-system controller box.

There was nothing surprising about the system. It was your standard ten-year-old Silent Knight alarm system. Documentation was strictly at the installer level. Motion detectors and sensors connect to these terminals, the alarm horn connects here, the phone line goes in here.

The PCB hardware included two microcontrollers that shared the control tasks. Because they had house numbers, Jeff and I concluded they were probably ROM-programmed 8051-family devices. And because it was ROM coded, we didn’t have a prayer of changing any internal operation. The best we could hope to do was monitor the external signals.

It would have been great if the alarm designers had taken a traditional engineering approach. Even a predictable approach would have been welcomed. In the world of high-volume consumer-quality electronics however, nothing works the way you expect it to, and "cute" is a term frequently used to describe the design technique.

The methodology is quite straightforward. Take a circuit that works the way you’d normally design it, throw away half the parts (or parts cost), and then make it do all the same control tasks. These are the guys who make a fine art of cycle-stealing, multiplexed operation, and hairy-edge qualification. Want them to design your next medical product?

This unit was no exception. The user interface consisted of a 3 ´ 4 keypad with a green LED (ready), a red LED (armed), and a single 7-segment LED display (zone). The keypad labels were 0–9, Door, and On/Off. Pressing any button makes an internal beeper sound. Photo 1 shows a close up of the alarm’s keypad.

Click here to enlarge)

Photo 1– The alarm system PIN is entered via a keypad.The ASDL system monitors and records the time and date of all key presses.

Similar to the operation of most alarm systems, the user looks for a green light indicating the system has no open doors and punches in a four-digit code followed by the on/off button. The alarm goes on, the red LED lights, and you have about 45 s to vacate the building. The process is reversed to shut off the alarm.

Jeff and I concluded the way for us to monitor entry and exit times and codes was to attach a circuit in parallel with this user interface and tap into its communication with the system box. Punch in 6637 and On, and we’d log it to a printer. The only sticky part was guessing where all these signals were so we could tell which key was pressed.

The keypad in the entryway connects to the system via an 11-wire parallel cable. The 3 ´ 4 keypad has four rows labeled 1–3, 4–6, 7–9, and Door, 0, and On/Off.

Electrically, we determined that the keys are scanned in two separate groups of six. Two opposite and alternating signals drive the two groups. Pressing none of the keys results in a logic 0 on the three column inputs back at the system board.

Pressing a key diode ORs one of the phases with one or more of the column inputs, like this: 1 = 001, 2 = 010, 3 = 011. A 7 also creates the 001 combination but in step with the opposite phase. The system knows which key is pressed based on the column inputs and the phase of the input signal.

Other signals to the entry panel enable the red or green LEDs and drive a piezo beeper when any key is pressed. All signals are at the 12-V level.